Gastrointestinal

Small bowel obstruction: imaging and management

Clinical Overview and When to Suspect Small Bowel Obstruction

— ~15% of ED admissions for acute abdominal pain in adults with prior surgery

— Accounts for ~300,000 US hospitalizations annually; mortality 2–8% uncomplicated, up to 25% with strangulation

— Adhesions (60–75%) — most common, prior abdominal/pelvic surgery

— Bulges (hernias, ~10–15%) — most common cause in patients without prior surgery

— Cancer (~10–15%) — intrinsic (small bowel adenocarcinoma, lymphoma) or extrinsic (carcinomatosis, ovarian)

— Less common: Crohn strictures, intussusception (lead point in adults), gallstone ileus, radiation enteritis, internal hernia (post-Roux-en-Y), volvulus

— Cramping periumbilical pain + vomiting (often bilious or feculent) + obstipation + abdominal distension

— Prior laparotomy or laparoscopy of any kind, even decades earlier

— Reducible/incarcerated groin bulge in a virgin abdomen

— Known peritoneal malignancy with new vomiting

— Proximal SBO → early copious vomiting, less distension, less obstipation

— Distal SBO → prominent distension, feculent emesis, late vomiting, marked obstipation

— Partial: continued passage of flatus/stool, often resolves nonoperatively

— Complete: no flatus, no stool, higher strangulation risk

Definition: Mechanical blockage of the small intestine causing proximal dilation, distal decompression, and disrupted transit; distinguish from ileus (functional, no mechanical lesion) and pseudo-obstruction.

Epidemiology and burden:

Etiology — remember "ABC" in adults:

When to suspect SBO clinically:

Proximal vs distal pattern:

Partial vs complete:

Board pearl: In a patient with no prior surgery and no hernia, assume malignancy or Crohn disease until proven otherwise — CT and oncologic workup are mandatory before labeling it "idiopathic adhesion."

Step 3 management anchor: Initial trifecta = NPO, NG decompression, IV isotonic fluids, then CT to triage operative vs nonoperative.

Presentation Patterns and Key History

— Crampy, colicky abdominal pain in waves every 4–5 min (proximal) to 15–20 min (distal); shift to constant severe pain suggests ischemia/strangulation

— Vomiting — bilious early, becoming feculent (bacterial overgrowth) in prolonged distal obstruction

— Obstipation — absence of flatus is more specific than absence of stool; stool already distal to obstruction may still pass for 12–24 h

— Abdominal distension — increases with distal location

— Prior abdominal/pelvic/gynecologic surgery (C-section, appendectomy, hysterectomy count) → adhesions

— Prior bariatric surgery, especially Roux-en-Y → internal hernia (Petersen defect) even years later

— Hernia history, recent change in a known bulge, sudden inability to reduce

— Cancer history — ovarian, colorectal, gastric, melanoma metastases, carcinomatosis

— Crohn disease flares, prior strictureplasty, biologic therapy

— Gallstone disease in elderly female with pneumobilia → gallstone ileus

— Radiation therapy to pelvis → radiation enteritis stricture

— Foreign body ingestion, bezoars (psychiatric, gastric surgery)

— Sudden severe constant pain

— Fever, tachycardia disproportionate to dehydration

— Hematemesis or bloody stool

— Rapid deterioration over hours

— Postoperative ileus (recent surgery, no transition point)

— Gastroparesis (diabetes, no distension)

— Acute mesenteric ischemia (AF, pain out of proportion, lactic acidosis)

— Large bowel obstruction (more obstipation early, less vomiting)

Cardinal symptom tetrad:

Targeted history questions for Step 3 stem recognition:

Red-flag history suggesting strangulation/closed loop:

Mimics to rule out from history:

Key distinction: A virgin abdomen with SBO mandates aggressive search for hernia (including obturator, femoral, Spigelian) and CT imaging — do not assume adhesions; the diagnostic yield for malignancy or hernia is high.

Board pearl: Feculent emesis = distal SBO with overgrowth, not colonic obstruction.

Physical Exam Findings and Hemodynamic Assessment

— Tachycardia and hypotension → volume depletion from third-spacing (liters sequestered in bowel lumen/wall)

— Fever >38°C, persistent tachycardia, or hypotension = concern for strangulation, perforation, or sepsis

— Orthostatic changes common from vomiting/NPO state

— Distension — more pronounced in distal obstruction; measure girth if uncertain

— Auscultation: early high-pitched "tinkling" hyperactive bowel sounds; late silent abdomen (decompensation)

— Palpation: diffuse tenderness without peritoneal signs in uncomplicated SBO

— Localized tenderness, guarding, rebound, rigidity → ischemia or perforation → emergent OR

— Palpable mass → tumor, intussusception, abscess, or closed-loop

— Visible peristalsis through thin abdominal wall in cachectic patients

— Inspect and palpate inguinal, femoral, umbilical, incisional, and obturator regions

— Howship-Romberg sign (medial thigh pain with hip extension/internal rotation) = obturator hernia, classically elderly thin women

— Reducibility, tenderness, skin changes over a bulge

— Empty vault supports complete obstruction

— Gross blood → ischemia, intussusception, malignancy

— Mass → rectal/pelvic tumor causing extrinsic compression

— Document all — even small port-site scars indicate adhesion risk

— HR >100, SBP <100, lactate >2, UOP <0.5 mL/kg/h → aggressive crystalloid bolus, foley, recheck

Vital signs — assess severity first:

Abdominal exam:

Hernia exam — mandatory every time:

Rectal exam:

Surgical scars:

Hemodynamic resuscitation triggers:

CCS pearl: On CCS, order vital signs, abdominal exam, rectal exam, and hernia exam on initial encounter; place 2 large-bore IVs, NS bolus 1–2 L, foley catheter, NG tube, NPO before advancing the clock to imaging.

Board pearl: Peritonitis on exam = stop imaging, go to OR. Do not delay for CT in the unstable patient with a rigid abdomen.

Diagnostic Workup — Initial Labs and Imaging

— CBC — leukocytosis with left shift; WBC >15 or bandemia raises strangulation concern

— BMP — hypokalemia, hypochloremia, metabolic alkalosis from vomiting (proximal); metabolic acidosis suggests ischemia

— BUN/Cr — prerenal azotemia from third-spacing

— Lactate — elevation (>2.5) concerning for bowel ischemia; normal does not exclude early strangulation

— Lipase to exclude pancreatitis mimic

— LFTs if gallstone ileus suspected

— Type and screen in case OR needed; coags if anticoagulated

— VBG for acid-base in sick patients

— Pregnancy test in reproductive-age women before imaging

— Sensitivity only 60–70%; useful when CT unavailable

— Dilated small bowel loops >3 cm, air-fluid levels >2.5 cm at different heights ("stepladder"), string of pearls sign

— Paucity of colonic gas supports complete SBO

— Free air under diaphragm → perforation → emergent OR

— Pneumobilia + SBO + ectopic gallstone = Rigler triad of gallstone ileus

— Increasingly used: dilated fluid-filled loops >2.5 cm, to-and-fro peristalsis, tanga sign

— Sensitivity ~92%, useful in pregnancy and ED triage

— Sensitivity 90–96%, specificity 96%

— Identifies transition point, cause, severity, and complications (closed loop, ischemia, perforation)

— Oral contrast not required and often delays care; IV contrast preferred unless contraindicated

Initial labs (all SBO suspects):

Plain abdominal radiographs (supine + upright or left lateral decubitus):

Point-of-care ultrasound (POCUS):

CT abdomen/pelvis with IV contrast — modality of choice:

Board pearl: Hypochloremic, hypokalemic metabolic alkalosis with paradoxical aciduria is the classic electrolyte signature of proximal SBO with prolonged emesis — replete with normal saline + KCl.

Step 3 management: Order CT abdomen/pelvis with IV contrast as the first definitive imaging — do not waste a clock-tick on KUB alone if CT is available.

Diagnostic Workup — Advanced and Confirmatory Studies

— Transition point — abrupt caliber change from dilated proximal to decompressed distal bowel; pathognomonic for mechanical SBO

— Small bowel feces sign — particulate material in dilated loops, marks region near transition

— Closed-loop obstruction — two adjacent transition points, U- or C-shaped dilated loop, mesenteric vessels converging ("whirl sign") → surgical emergency

— Ischemia signs: bowel wall thickening, pneumatosis intestinalis, portal venous gas, lack of mural enhancement, mesenteric edema, free fluid

— Pneumoperitoneum → perforation

— Cause clues: hernia sac contents, mass, intussusception (target sign), gallstone with pneumobilia

— For adhesive partial SBO without ischemia/peritonitis after 12–24 h of failed NG decompression

— Give 100 mL Gastrografin via NG, clamp 30 min, then KUB at 8 and 24 h

— Contrast reaching colon within 24 h predicts successful nonoperative resolution (sensitivity ~96%)

— Hyperosmolar effect draws fluid into lumen → may itself relieve partial obstruction

— Contraindicated if peritonitis, perforation, complete obstruction with ischemia signs

CT findings to recognize and report:

Water-soluble contrast challenge (Gastrografin) — both diagnostic and therapeutic:

MR enterography: reserved for Crohn workup, pregnancy, or recurrent SBO of unclear cause

Capsule endoscopy/small bowel follow-through: outpatient evaluation of recurrent SBO or suspected stricture — contraindicated in acute obstruction (capsule retention)

Colonoscopy: if large bowel obstruction or distal lesion suspected on CT

Key distinction: Closed-loop obstruction = emergent OR regardless of how stable the patient looks; the loop can infarct within hours despite a benign abdominal exam.

Board pearl: Gastrografin does not cure complete or strangulated SBO — it is a triage tool for adhesive partial SBO without peritonitis.

Step 3 management: If CT shows closed-loop or ischemia signs → consult surgery emergently, do not attempt Gastrografin.

Risk Stratification and First-Line Management Logic

— 1. Is the patient unstable or peritonitic? → resuscitate + emergent OR

— 2. Is there strangulation, closed loop, or ischemia on CT? → emergent OR

— 3. Is there a complete obstruction with no transition through? → OR within 24 h

— 4. Is there an incarcerated hernia? → reduce or operate

— 5. Is this adhesive partial SBO without ischemia? → nonoperative trial 24–72 h

— Peritonitis, hemodynamic instability, perforation

— Closed-loop obstruction

— Strangulated hernia (irreducible + tender + skin changes)

— CT evidence of ischemia (pneumatosis, portal gas, wall thickening, lack of enhancement)

— Volvulus

— Virgin abdomen SBO (most have surgical etiology)

— Prior abdominal surgery

— Partial obstruction on CT

— No peritonitis, stable vitals, normal lactate

— Tolerable pain on conservative therapy

— NPO, NG tube to low intermittent suction

— IV isotonic fluids (NS or LR) with K replacement

— Foley for UOP monitoring

— Serial abdominal exams q4–6h

— Trend WBC, lactate, electrolytes

— Gastrografin challenge at 24–48 h if no clinical improvement

— ~65–80% of adhesive partial SBO resolves nonoperatively

— If no resolution by 72 h, operative intervention is warranted (longer waits increase strangulation risk and don't improve outcomes)

Decision algorithm — five questions at the bedside:

Indications for immediate surgery:

Indications for nonoperative management (adhesive SBO):

Nonoperative bundle (the "tincture of time" approach):

Success rates:

CCS pearl: Build the order set early: NPO, NG to LIS, IV NS at 125 mL/h after bolus, KCl repletion, foley, serial abdominal exams q4h, surgery consult, CBC/BMP/lactate q12h. Advance clock in 6–12 h blocks and reassess.

Board pearl: >72 h of failed nonoperative management = operate. Prolonging makes things worse, not better.

Pharmacotherapy and Supportive Medical Management

— Isotonic crystalloid: lactated Ringer's preferred (avoids hyperchloremic acidosis); 1–2 L bolus then maintenance based on UOP (target 0.5 mL/kg/h)

— Severe dehydration (HR >120, SBP <90): aggressive resuscitation with reassessment q15 min

— Avoid hypotonic fluids — exacerbate hyponatremia from vomiting

— Potassium: vomiting drives losses; replace IV when K <3.5, oral inappropriate (NPO)

— Magnesium: replete to >2.0 to facilitate K correction

— Chloride: NS corrects hypochloremic alkalosis

— IV opioids (morphine, hydromorphone, fentanyl) titrated; do not withhold for fear of masking exam — modern practice supports analgesia + serial exams

— Avoid NSAIDs (ulcer/bleeding risk in sick gut)

— Reassess pain pattern — escalating constant pain raises ischemia concern

— NG decompression is primary; ondansetron 4 mg IV for breakthrough nausea

— Avoid metoclopramide/erythromycin (prokinetics) — contraindicated in mechanical obstruction

— Not routine for uncomplicated SBO

— Indicated preoperatively (cefoxitin, cefotetan, or piperacillin-tazobactam) covering gram-negative + anaerobes

— Indicated for suspected strangulation, perforation, or sepsis

— SCDs + chemical prophylaxis (enoxaparin 40 mg SC daily) unless bleeding or imminent surgery; SBO patients are high-risk for DVT

— PPI (pantoprazole 40 mg IV) reasonable in ICU-level patients or prolonged NG

— NPO acutely; if nonoperative course >7 days expected, initiate TPN

Fluid resuscitation — the cornerstone:

Electrolyte replacement:

Analgesia:

Antiemetics:

Antibiotics:

VTE prophylaxis:

Stress ulcer prophylaxis:

Nutrition:

Board pearl: Prokinetics (metoclopramide, erythromycin) are contraindicated in mechanical SBO — they worsen pain and risk perforation. Use only in confirmed ileus.

Step 3 management: Hold/adjust home meds: hold diuretics, ACE-I (renal protection in volume depletion), metformin (hold periop, lactic acidosis risk), oral diabetes meds (NPO → insulin sliding scale).

Surgical and Procedural Management

— 14–18 Fr Salem sump to low intermittent suction

— Confirm placement by auscultation + radiograph

— Document output q4–6h; >1.5 L in 24 h reflects significant obstruction

— Removed when output <500 mL/day + bowel function returns + clinical improvement

— Manual reduction of non-strangulated incarcerated hernia in ED is appropriate; surgical repair during same admission

— Strangulated hernia → emergent OR (no manual reduction — risk of reducing ischemic bowel into peritoneum)

— Laparoscopic adhesiolysis — preferred when feasible (less ileus, shorter LOS, less recurrent adhesions); contraindicated with severe distension or hemodynamic instability

— Open laparotomy — for complex, multiloop obstruction, ischemia, malignancy

— Bowel resection with primary anastomosis for ischemic/non-viable segments; assess viability after warm packing 10 min — pink color, peristalsis, palpable pulses, Doppler signal

— Damage control laparotomy with temporary closure if hemodynamically unstable or extensive ischemia

— Stricturoplasty or limited resection for Crohn strictures (bowel preservation)

— Palliative bypass or venting gastrostomy in unresectable carcinomatosis

— Gallstone ileus: enterolithotomy alone (vs. one-stage with cholecystectomy/fistula repair) — staged approach in frail elderly

— Internal hernia post-Roux-en-Y: reduction + mesenteric defect closure

— Adhesive SBO: minimize adhesiolysis to symptomatic areas

— Early ambulation, gum chewing, multimodal analgesia, opioid-sparing (ERAS)

— Advance diet as tolerated when flatus returns

— Continue VTE prophylaxis

NG tube decompression:

Hernia reduction:

Surgical approaches:

Specific scenarios:

Postoperative care:

CCS pearl: When operating, the order sequence is: type & cross, preop antibiotics (cefoxitin 2 g IV) within 60 min of incision, foley, NG, consent, mark site, OR. Postop: advance clock, then reassess vitals, UOP, NG output, pain control.

Board pearl: Laparoscopic approach for adhesive SBO has lower morbidity but higher conversion rate (~30%) — patient counseling should reflect this.

Special Populations — Elderly and Renal/Hepatic Impairment

— Higher mortality (10–20%) from comorbidities, delayed presentation, atypical features

— Atypical presentations: less pain, less fever, blunted WBC response; may present with confusion, falls, hypotension

— Lower threshold for CT — exam less reliable

— Specific etiologies more common: gallstone ileus (elderly women), obturator hernia (thin elderly women), colorectal/ovarian malignancy, sigmoid volvulus mimicking SBO

— Frailty assessment before surgery (Clinical Frailty Scale) — guides goals of care discussion

— Polypharmacy — review anticoagulants (hold warfarin, bridge if needed; DOACs require timing for surgery), antiplatelets

— Delirium (prevent with reorientation, sleep hygiene, minimize benzos/anticholinergics, treat pain)

— Pneumonia, DVT, pressure injury

— Functional decline — early PT/OT consult

— Avoid IV contrast if eGFR <30 unless ischemia suspected and outweighs risk; use non-contrast CT or MR enterography alternatives

— Resuscitation: isotonic crystalloid but monitor for volume overload in CKD/HF

— Drug dose adjustments: opioids (avoid morphine, prefer fentanyl/hydromorphone), enoxaparin renal-dose (30 mg SC daily if CrCl <30), avoid NSAIDs

— Hold metformin for ≥48 h with contrast or surgery

— Hold SGLT2 inhibitors 3 days preop (euglycemic DKA risk)

— Coagulopathy → check INR, transfuse FFP/vitamin K before surgery

— Albumin <2.5 portends poor wound healing

— Avoid acetaminophen >2 g/day, avoid sedatives that precipitate encephalopathy

— Ascites complicates fluid management — monitor closely

Elderly considerations:

Postoperative risks in elderly:

Renal impairment:

Hepatic impairment:

Board pearl: Obturator hernia = elderly thin woman with bowel obstruction + Howship-Romberg sign + virgin abdomen. Always palpate medial thigh and image with CT.

Step 3 management: In an elderly SBO patient on warfarin needing emergent surgery: reverse with 4-factor PCC + IV vitamin K 10 mg; FFP only if PCC unavailable.

Special Populations — Pregnancy, Pediatrics, and Other Subgroups

— SBO in pregnancy is rare but mortality up to 20% maternal, 30% fetal due to delayed diagnosis

— Most common in 3rd trimester or postpartum; adhesions still leading cause

— Symptoms mimic normal pregnancy; high index of suspicion needed

— Imaging: ultrasound first, then MRI without gadolinium — preferred over CT; if CT needed for life-threatening concern, do not withhold (single-dose radiation 25 mGy below teratogenic threshold)

— Surgical management not deferred for pregnancy when indicated; left lateral decubitus positioning intraop, fetal monitoring, OB co-management

— Avoid teratogenic drugs (warfarin, fluoroquinolones in 1st trimester preference, metronidazole acceptable)

— Neonate: intestinal atresia, malrotation with midgut volvulus, meconium ileus (CF), Hirschsprung, NEC

— Infant (3 mo–3 yr): intussusception (ileocolic, idiopathic or after viral illness/rotavirus vaccine) — currant jelly stool, sausage mass, target sign on US; air or contrast enema is diagnostic + therapeutic

— Older children: adhesions (post-appendectomy), incarcerated inguinal hernia, Meckel diverticulum with band, intussusception with pathologic lead point (lymphoma, polyp)

— Malrotation with midgut volvulus = surgical emergency in any age; bilious emesis in a neonate = malrotation until proven otherwise → upper GI series

— Recurrent stricture-related SBO; consider medical optimization (steroids, biologics) before surgery for inflammatory strictures; fibrotic strictures need resection or stricturoplasty

— Malignant bowel obstruction (MBO): consider octreotide, dexamethasone, antiemetics, venting PEG; surgery only if reasonable life expectancy and good performance status

Pregnancy:

Pediatrics — etiology differs by age:

Crohn disease patients:

Cancer/palliative patients:

Board pearl: Bilious emesis in a neonate = malrotation with midgut volvulus until proven otherwise — emergent upper GI contrast study, then OR.

Key distinction: In pregnancy with possible SBO, do not delay imaging or surgery out of radiation concern — maternal death from delayed diagnosis is the larger threat.

Complications and Adverse Outcomes

— Closed-loop obstruction or prolonged distension compromises mesenteric perfusion

— Progresses from venous congestion → arterial compromise → infarction → perforation

— Mortality jumps from <5% (simple SBO) to 25–30% (strangulated)

— Signs: tachycardia, fever, leukocytosis, peritonitis, lactic acidosis, CT findings of pneumatosis/portal gas

— Free air on imaging, diffuse peritonitis, septic shock

— Requires emergent OR with resection + washout

— From translocation or perforation; manage per Surviving Sepsis bundle: broad-spectrum antibiotics within 1 h, lactate, blood cultures, fluid resuscitation, source control

— Vomiting with depressed mental status; NG decompression dramatically reduces risk

— Head of bed elevation >30°, secure airway in obtunded patients

— Hypokalemic hypochloremic metabolic alkalosis (proximal SBO)

— Metabolic acidosis with elevated lactate suggests ischemia

— Hypovolemic shock from third-spacing

— Prerenal from hypovolemia; corrects with resuscitation

— Contrast-associated AKI in CKD patients

— Anastomotic leak (POD 5–7): fever, tachycardia, increased drain output, ileus prolonged

— Surgical site infection, wound dehiscence

— Postop ileus (vs recurrent SBO) — distinguish by CT

— Short bowel syndrome after extensive resection (<200 cm small bowel) — TPN, vitamin/mineral deficiencies, oxalate stones

— Enterocutaneous fistula — management: nutrition, source control, octreotide; "SNAP" — Sepsis, Nutrition, Anatomy, Plan

— Recurrent adhesive SBO — lifetime risk ~30% after one episode, higher with each subsequent

Bowel ischemia and strangulation:

Perforation and peritonitis:

Sepsis and septic shock:

Aspiration pneumonitis:

Electrolyte and acid-base derangements:

Acute kidney injury:

Postoperative complications:

Board pearl: Lactate elevation in SBO is a late finding of ischemia. A normal lactate does not exclude strangulation; clinical and CT findings drive the decision.

CCS pearl: When postop fever spikes on day 5–7, order CT abdomen/pelvis with PO + IV contrast to rule out anastomotic leak — don't blame atelectasis.

When to Escalate Care — ICU, Consult, and Triage

— All confirmed SBO get surgical consultation; nonoperative trial is a surgical decision, not a medical one

— Document discussion and shared plan

— Hemodynamic instability requiring vasopressors or aggressive resuscitation

— Septic shock or suspected ischemia

— Lactic acidosis, pH <7.3, lactate >4

— Respiratory failure (aspiration pneumonitis)

— Post-emergent laparotomy with damage control / open abdomen

— Significant comorbidity decompensation (HF exacerbation, AKI requiring CRRT)

— Peritonitis on exam

— Pneumoperitoneum

— Closed-loop obstruction on CT

— Strangulated hernia

— Hemodynamic instability with abdominal source

— Failed nonoperative management beyond 72 h

— Hemodynamically stable adhesive partial SBO on nonoperative trial

— Postoperative day 1+ after uncomplicated lysis of adhesions

— Surgical oncology — known/suspected malignancy

— Gastroenterology — Crohn-related, endoscopic stent placement for malignant obstruction

— Interventional radiology — percutaneous drainage of abscess, venting gastrostomy

— Palliative care — malignant bowel obstruction, goals of care

— Nutrition — anticipated prolonged NPO or short bowel

— Geriatrics — frail elderly preop optimization

— If community hospital lacks 24/7 surgical coverage, advanced imaging, or ICU, transfer before decompensation

— Document EMTALA-compliant transfer with sending and receiving physician communication

Surgery consult — call early, every time:

Indications for ICU admission:

Indications for emergent OR (do not delay for further imaging):

Indications for stepdown/floor:

Specialty consults to consider:

Transfer considerations:

Step 3 management: Surgical consultation should be obtained at the time of SBO diagnosis, even if nonoperative management is planned — this is the standard of care and prevents delays if patient deteriorates.

Board pearl: A patient on nonoperative trial who develops new tachycardia, leukocytosis, fever, or worsening pain needs immediate reassessment with repeat exam, labs, and likely repeat CT — these signal failure of conservative management.

Key Differentials — Same-Category Causes (Bowel Obstruction Mimics)

— Functional, no mechanical lesion; post-op, electrolyte abnormalities (hypokalemia, hypomagnesemia), opioids, sepsis, retroperitoneal hematoma

— Exam: distension without colic, diffuse decreased bowel sounds, less vomiting

— Imaging: diffusely dilated small and large bowel without transition point

— Management: correct underlying cause, electrolytes, minimize opioids, ambulation, alvimopan post-op

— Cancer (most common, sigmoid/rectosigmoid), volvulus (sigmoid, cecal), diverticular stricture

— Distension prominent, vomiting late, obstipation early

— CT shows dilated colon (>6 cm cecum >9 cm); cecal diameter >12 cm risks perforation

— Sigmoid volvulus → "coffee bean" sign → endoscopic detorsion + elective sigmoidectomy

— Cecal volvulus → operative

— Massive colonic dilation without mechanical obstruction

— Hospitalized/postop patients, electrolyte derangements, opioids

— Treatment: decompression, electrolyte correction, neostigmine 2 mg IV if cecum >12 cm and no perforation/ischemia (monitor for bradycardia, have atropine ready)

— Vomiting without bile, succussion splash, peptic ulcer disease or gastric/pancreatic malignancy

— EGD diagnostic and often therapeutic

— Already covered as a surgical emergency variant; specifically arises from hernia, adhesive band, or volvulus

— Usually has pathologic lead point (tumor, polyp, Meckel) — unlike pediatric (usually idiopathic)

— Surgical resection without reduction (don't risk seeding malignancy)

— High suspicion in any post-RYGB patient with abdominal pain even without classic obstruction signs

— CT may show whirl sign of mesentery; surgical exploration even with subtle findings

Paralytic (adynamic) ileus:

Large bowel obstruction (LBO):

Acute colonic pseudo-obstruction (Ogilvie syndrome):

Gastric outlet obstruction:

Closed-loop SBO:

Intussusception in adults:

Internal hernia (post-bariatric):

Key distinction: Ileus has no transition point on CT and involves both small and large bowel; mechanical SBO has a discrete transition point with decompressed bowel distally.

Board pearl: Neostigmine for Ogilvie syndrome — telemetry monitoring, exclude mechanical obstruction first, do not give in pregnancy or recent MI.

Key Differentials — Other-Category Causes

— Pain out of proportion to exam, AF (embolic), atherosclerosis (thrombotic), hypotension (non-occlusive)

— Lactic acidosis early, leukocytosis, hemoconcentration

— CT angiography is diagnostic; emergent vascular surgery / IR thrombectomy + revascularization

— Distinction from SBO: ischemia has minimal distension early, severe pain disproportionate to findings

— Epigastric pain radiating to back, vomiting, elevated lipase >3x ULN

— Can cause sentinel loop or paralytic ileus mimicking SBO on KUB

— CT distinguishes

— RUQ pain, Murphy sign, fever, jaundice (cholangitis)

— Imaging: US first, then HIDA or MRCP

— LLQ pain, fever; abscess may cause partial obstruction

— CT diagnostic; antibiotics + percutaneous drainage

— RLQ pain; can cause local ileus

— CT for diagnosis

— Reproductive-age woman with pelvic pain, fever; cervical motion tenderness

— Ultrasound, CT pelvis; antibiotics ± drainage

— Vomiting, abdominal pain can mimic surgical abdomen

— Check glucose, anion gap, ketones; cortisol/ACTH if adrenal concern

— Rare but classic mimics — recurrent unexplained abdominal pain, neuropsychiatric features

— Urine porphobilinogen for AIP; blood lead level

— Elderly, opioid-induced; rectal exam reveals impaction

— Distinguish from LBO by CT and digital exam

— Younger patients, normal imaging, history of chronic cannabis use, hot showers relieve symptoms

— Reproductive-age woman, sudden severe pelvic pain, vomiting; pelvic US with Doppler diagnostic

Acute mesenteric ischemia:

Acute pancreatitis:

Cholecystitis / cholangitis:

Diverticulitis with abscess:

Appendicitis with phlegmon:

Pelvic inflammatory disease / tubo-ovarian abscess:

DKA / adrenal crisis:

Lead poisoning, porphyria:

Constipation / fecal impaction:

Functional / cyclic vomiting / cannabinoid hyperemesis:

Ovarian torsion:

Board pearl: AF + severe abdominal pain + minimal exam findings + elevated lactate = mesenteric ischemia until proven otherwise — get CTA, do not waste time on KUB.

Key distinction: SBO pain is crampy/colicky and follows distension; mesenteric ischemia pain is constant, severe, and disproportionate to exam.

Secondary Prevention, Discharge, and Long-Term Plan

— Tolerating diet (advanced from clears → regular)

— Bowel function returned (flatus, BM)

— NG tube removed >24 h with no recurrent distension

— Pain controlled on oral analgesics

— Stable vitals, normal labs, no fever

— Mobilizing independently or at preadmission baseline

— Bowel regimen: docusate + senna scheduled, especially if on opioids; lactulose or PEG 3350 PRN

— Analgesia: transition to acetaminophen-based regimen; limit opioid prescription to 3–5 days with naloxone co-prescription per state mandate where applicable

— VTE prophylaxis post-op: consider extended (28 days) enoxaparin after cancer-related surgery

— PPI: continue if NG was prolonged or stress ulcer concern

— Resume home meds: metformin once eating + renal function back to baseline; anticoagulation per bridging protocol

— Adhesion barrier (Seprafilm) intraoperatively reduces but does not eliminate adhesion formation

— Laparoscopic approach when feasible reduces adhesions

— Hernia repair during index admission for incarcerated hernia

— For recurrent adhesive SBO, consider elective laparoscopic adhesiolysis in selected cases (controversial)

— Malignancy-related SBO: oncology follow-up, consider chemotherapy, palliative planning

— Crohn-related: biologic therapy optimization, GI follow-up, surveillance colonoscopy

— Short bowel syndrome: parenteral nutrition planning, teduglutide (GLP-2 analog) for intestinal rehab, vitamin B12 supplementation if terminal ileum resected

— Avoid large fibrous boluses (e.g., persimmons, unchewed vegetables in patients with prior strictures or gastric surgery → phytobezoars)

— Hydration, regular bowel habits

Discharge readiness criteria:

Discharge medications:

Recurrence prevention:

Long-term considerations:

Lifestyle counseling:

Board pearl: After terminal ileum resection >60 cm, lifelong vitamin B12 (IM or high-dose oral) is required; also monitor bile salt diarrhea (cholestyramine) and fat-soluble vitamin deficiencies.

Step 3 management: Schedule surgical follow-up at 2 weeks, PCP at 4 weeks, oncology if malignant, GI if Crohn — and ensure communication of imaging/pathology results across the transition of care.

Follow-Up, Monitoring Parameters, and Counseling

— Surgical clinic at 10–14 days post-discharge for wound check, pathology review, drain removal if applicable

— Primary care at 4 weeks for medication reconciliation, comorbidity recheck, functional status

— Oncology referral within 2 weeks if malignant pathology identified

— GI/IBD specialist for Crohn-related SBO

— Open laparotomy: keep dry 48 h, monitor for erythema, dehiscence, drainage

— Surgical staples removed 10–14 days; sutures 7–10 days

— Educate on signs of SSI (fever, redness, purulent drainage)

— No lifting >10 lbs for 6 weeks post-laparotomy (incisional hernia risk)

— Laparoscopic: lighter restrictions, often 2–4 weeks

— Driving when off opioids and able to perform emergency stop

— Return to work depends on occupation; sedentary 2 weeks, manual labor 6–8 weeks

— Weight at each follow-up; expect 5–10 lb loss post-op, should stabilize

— Albumin, prealbumin if concerns about malnutrition

— Short bowel: stool output, electrolytes weekly initially

— Return to ED for inability to tolerate PO, persistent vomiting, severe distension, no flatus/BM >24 h, fever, severe pain

— Postoperative depression and anxiety common; screen with PHQ-2 at follow-up

— Cancer-related SBO patients particularly vulnerable

— Anticoagulation reinitiation timing post-op (typically 48–72 h if hemostasis adequate)

— Diabetes: HbA1c at 3 months, glucose logs in interim

— Smoking cessation counseling — improves wound healing, reduces recurrence

Follow-up cadence:

Wound and incision care:

Activity restrictions:

Nutrition monitoring:

Recurrence red flags — patient counseling:

Mental health and recovery:

Special monitoring:

CCS pearl: Always close the loop on outpatient orders — schedule the follow-up appointment, send the consult, prescribe the bowel regimen, and counsel return precautions before discharging on CCS.

Board pearl: Incisional hernia complicates 10–20% of midline laparotomies; counsel weight loss, smoking cessation, and lifting restrictions to reduce risk.

Ethical, Legal, and Patient Safety Considerations

— Discuss possibility of bowel resection, ostomy creation, intraoperative findings (cancer, ischemia), and possibility of staged procedures

— In incapacitated patients (sepsis, obtundation): proceed with emergency doctrine / implied consent for life-saving surgery; document attempts to reach surrogate

— Use surrogate decision-maker hierarchy if patient lacks capacity

— Carcinomatosis with poor performance status: aggressive surgery often does not extend or improve quality of life

— Palliative care consultation for goals-of-care discussion, advance directives, code status

— Consider venting gastrostomy, octreotide, dexamethasone for symptom management

— Avoid futile heroic interventions; document discussions

— Wrong-site/wrong-procedure prevention: time-out before incision, site marking, surgical safety checklist (WHO)

— Retained surgical items: sponge and instrument counts pre/post; intraop X-ray if discrepancy

— VTE prophylaxis omission is a "never event"-adjacent miss; SBO patients are very high risk

— Medication reconciliation at admission, transfer, and discharge — especially anticoagulants and diabetes meds

— Handoff communication at shift change using structured tools (SBAR, I-PASS) — failure to communicate worsening exam findings to next team is a major source of malpractice

— Discharge with incomplete bowel function, no follow-up scheduled, or failure to communicate pathology results → bounce-back admission

— Ensure receiving outpatient provider has discharge summary within 48 h

— Suspected abuse/neglect in elderly with SBO from intentional foreign body or feeding neglect

— Document refusal of recommended surgery and risks discussed

— Avoid serial KUBs when CT or clinical exam suffices

— Gastrografin protocol shortens hospital LOS

Informed consent in emergent SBO surgery:

Goals of care in malignant bowel obstruction:

Patient safety priorities:

Transitions of care risks:

Mandatory reporting and documentation:

Resource stewardship:

Step 3 management: When a patient with MBO from end-stage ovarian cancer asks "should we operate?" — the answer involves shared decision-making with palliative care input, not reflexive surgery. Document the conversation.

Board pearl: Failure to obtain timely surgical consultation in SBO is a recurring source of malpractice claims — consult early, document the discussion, even on nonoperative trials.

High-Yield Associations and Rapid-Fire Clinical Facts

Adhesions = #1 cause of SBO in adults with prior surgery

Hernias = #1 cause in patients with no surgical history

Malignancy = think carcinomatosis or new primary if virgin abdomen + no hernia

Crohn disease = stricturing terminal ileum; consider strictureplasty

Bilious emesis in neonate = malrotation + midgut volvulus; upper GI series

Currant jelly stool + sausage mass + target sign = intussusception in infant; air enema

Howship-Romberg sign = obturator hernia in thin elderly women

Rigler triad = pneumobilia + SBO + ectopic gallstone = gallstone ileus

Sister Mary Joseph nodule = periumbilical mass = intra-abdominal malignancy

Whirl sign on CT = closed-loop obstruction or volvulus; surgical emergency

Pneumatosis intestinalis + portal venous gas = bowel ischemia; emergent OR

Small bowel feces sign = marks transition point in chronic SBO

Coffee bean sign = sigmoid volvulus on KUB

String of pearls = air-fluid levels in dilated small bowel loops on upright KUB

Stepladder appearance = dilated loops at varying heights with air-fluid levels

Gastrografin reaching colon in 24 h = predicts nonoperative success

Closed-loop obstruction = always operate, even if patient looks well

Post-Roux-en-Y abdominal pain = internal hernia until proven otherwise

Hypokalemic hypochloremic metabolic alkalosis = proximal SBO with prolonged vomiting

Metabolic acidosis with elevated lactate = bowel ischemia → emergent OR

>72 hours failed nonoperative management = operate

Lifetime adhesive SBO recurrence = ~30% after first episode

Terminal ileum resection >60 cm = lifelong B12, bile salt diarrhea, B12/D/oxalate stones

Short bowel <200 cm = consider TPN and teduglutide

Pregnancy SBO = MRI without gadolinium preferred; don't delay surgery

Neostigmine = treatment for Ogilvie (pseudo-obstruction), NOT mechanical SBO

Prokinetics (metoclopramide) = contraindicated in mechanical SBO

Step 3 board favorite: Patient with Roux-en-Y 5 years ago presenting with abdominal pain and minimal CT findings → laparoscopy for internal hernia even if imaging looks subtle

Board pearl: When a question stem mentions prior C-section + cramping pain + bilious vomiting + air-fluid levels — pick NG decompression + IV fluids + surgical consult, not immediate OR, unless ischemia signs are present.

Board Question Stem Patterns

— "52-year-old woman with prior hysterectomy presents with 2 days of crampy abdominal pain, bilious emesis, and abdominal distension. KUB shows dilated small bowel loops with air-fluid levels."

— Answer: NPO, NG tube, IV fluids, surgery consult, CT abdomen/pelvis

— "68-year-old man with painful, tender groin bulge that he can no longer push back in, plus vomiting."

— Answer: Emergent surgical repair; do not attempt manual reduction

— "Patient with SBO on CT shows U-shaped dilated loop with mesenteric whirl and adjacent transition points."

— Answer: Emergent laparotomy regardless of stability

— "78-year-old woman with pneumobilia on CT, dilated SB loops, and ectopic gallstone in distal ileum."

— Answer: Enterolithotomy

— "45-year-old man with no prior surgery presents with SBO; CT shows mass at transition point."

— Answer: Surgical exploration with resection (likely malignancy)

— "Patient 3 years post-Roux-en-Y with intermittent severe abdominal pain; CT shows mesenteric swirl."

— Answer: Diagnostic laparoscopy

— "Newborn with bilious emesis on day 3 of life."

— Answer: Upper GI contrast study, then OR for Ladd procedure

— "10-month-old with intermittent crying, drawing legs up, currant jelly stool, sausage abdominal mass."

— Answer: Air contrast enema (diagnostic + therapeutic)

— "Postop day 3 patient with distension, no flatus, CT shows diffusely dilated small AND large bowel without transition."

— Answer: Ileus — supportive care, electrolyte correction

— "Patient on NG decompression and IV fluids for 4 days without improvement, Gastrografin failed to reach colon."

— Answer: Operative intervention

— "Hospitalized patient with massive colonic dilation, cecum 13 cm, no mechanical obstruction."

— Answer: Neostigmine after excluding perforation

Pattern 1 — Classic adhesive SBO:

Pattern 2 — Strangulated hernia:

Pattern 3 — Closed-loop obstruction:

Pattern 4 — Gallstone ileus:

Pattern 5 — Virgin abdomen SBO:

Pattern 6 — Internal hernia post-bypass:

Pattern 7 — Malrotation in neonate:

Pattern 8 — Intussusception in infant:

Pattern 9 — Ileus vs. SBO:

Pattern 10 — Failed nonoperative trial:

Pattern 11 — Ogilvie syndrome:

Board pearl: Look for the transition point in CT-based stems — its presence (and location) defines mechanical SBO and points to etiology.

Step 3 management: When the stem describes worsening tachycardia, fever, and rising WBC during a nonoperative trial — the right answer is almost always operate now, not "continue current management."

One-Line Recap

— Diagnostic anchor: CT abdomen/pelvis with IV contrast — find the transition point; look for ischemia signs (pneumatosis, portal gas, whirl sign, lack of enhancement, free fluid)

— Initial bundle (every SBO): NPO, NG to LIS, IV isotonic fluids, foley, K/Mg repletion, IV analgesia, serial exams, surgery consult at diagnosis

— Operate immediately for: peritonitis, closed loop, strangulated hernia, perforation, ischemia, instability, virgin abdomen with mass, or failed nonoperative trial >72 h

— Special populations: bilious emesis in neonate = malrotation; sausage mass in infant = intussusception; post-RYGB pain = internal hernia; AF + disproportionate pain = mesenteric ischemia (not SBO); pregnant patient = MRI first but never delay needed surgery

— Discharge essentials: tolerating diet, bowel function, bowel regimen, surgical follow-up 2 weeks, communicate pathology, counsel return precautions

The core teaching: Small bowel obstruction is diagnosed clinically (colicky pain, vomiting, obstipation, distension — usually with a surgical history or hernia) and confirmed by CT with IV contrast showing a transition point; management hinges on rapidly distinguishing uncomplicated partial adhesive SBO (NPO, NG decompression, IV fluids, electrolyte repletion, surgical consult, and Gastrografin trial) from complicated SBO (closed loop, strangulation, ischemia, peritonitis, perforation, or strangulated hernia) which mandates emergent operative intervention.

Rapid recap bullets:

Board pearl: When in doubt between continued conservative management and surgery in a deteriorating SBO patient — operate; delayed laparotomy for strangulation is one of the most lethal misjudgments in acute care surgery and a perennial Step 3 distractor trap.