Perioperative & Surgical Care

Acute abdomen: differential and workup

Clinical Overview and When to Suspect Acute Abdomen

— Perforated viscus (peptic ulcer, diverticulum, appendix, colon cancer)

— Bowel obstruction with strangulation or ischemia

— Mesenteric ischemia (especially elderly with AFib)

— Ruptured AAA (>50 yo, hypotension, back/flank pain)

— Ectopic pregnancy rupture (any reproductive-age woman)

— Acute appendicitis, cholecystitis, ascending cholangitis

— Incarcerated/strangulated hernia

— Hemodynamic instability (SBP <90, HR >120)

— Peritoneal signs (rigidity, rebound, guarding)

— Pain out of proportion to exam (think mesenteric ischemia)

— Fever >38.5°C with localized tenderness

— Hematochezia, melena, or coffee-ground emesis with pain

— Pulsatile abdominal mass

— Pain with syncope (ruptured ectopic, ruptured AAA, splenic rupture)

— Elderly: vascular catastrophes, malignancy, atypical presentations

— Reproductive-age women: always βhCG before imaging or analgesia decisions

— Immunosuppressed/diabetic: blunted signs, lower threshold for CT

— Cirrhotic with ascites: SBP must be ruled out via paracentesis

Step 3 management: In a CCS case, the first three orders for any acute abdomen are IV access × 2, NPO, and stat labs + upright CXR/CT abdomen — and in women of reproductive age, βhCG before any imaging or opioid. Failure to order βhCG is a classic point deduction.

Definition: Sudden onset of severe abdominal pain (<7 days, usually <48 hours) requiring urgent evaluation to exclude a surgical or life-threatening cause

Core question for Step 3: Does this patient need the OR, the IR suite, the ICU, or can they be observed/discharged with outpatient follow-up?

Major surgical etiologies to suspect early:

Non-surgical mimics: Inferior MI, lower-lobe pneumonia, DKA, adrenal crisis, sickle cell crisis, porphyria, familial Mediterranean fever, lead toxicity, herpes zoster

Red flags mandating immediate workup:

Demographic anchors:

Presentation Patterns and Key History

— Onset: Sudden "thunderclap" → perforation, ruptured AAA, ruptured ectopic, embolic mesenteric ischemia. Gradual crescendo → appendicitis, cholecystitis, diverticulitis, SBO

— Location and migration:

– Periumbilical → RLQ: appendicitis

– Epigastric → RUQ/back: cholecystitis, pancreatitis

– Diffuse → localized: progressing peritonitis

– Flank → groin: nephrolithiasis

– Tearing back/flank: AAA dissection/rupture

— Quality: Colicky (intermittent crescendo) suggests hollow viscus obstruction (SBO, ureteral stone, biliary colic). Constant boring → pancreatitis, ischemia. Burning → PUD, esophagitis

— Radiation: Scapular tip → diaphragmatic irritation (cholecystitis, perforation, splenic). Groin → ureter/AAA. Back → pancreatitis, AAA, posterior ulcer

— Timing relative to food: Postprandial pain → biliary, mesenteric angina, gastric ulcer. Pain relieved by food → duodenal ulcer

— Vomiting BEFORE pain → gastroenteritis (vs. pain before vomiting → surgical abdomen)

— Feculent emesis → distal SBO or colonic obstruction with incompetent ileocecal valve

— Obstipation (no flatus/stool) → complete bowel obstruction

— Hematochezia + pain in elderly → ischemic colitis or mesenteric ischemia

— Jaundice + RUQ pain + fever = Charcot triad (cholangitis); add hypotension + AMS = Reynolds pentad

— AFib or recent MI → mesenteric embolism

— Prior abdominal surgery → adhesive SBO (most common cause)

— IBD → toxic megacolon, perforation, abscess

— NSAID or steroid use → perforated peptic ulcer

— Alcohol use → pancreatitis

— Last menstrual period → ectopic, ovarian torsion

Board pearl: "Pain out of proportion to exam" + AFib + lactic acidosis = acute mesenteric ischemia until proven otherwise. Get CT angiography immediately — don't wait for peritoneal signs, by then the bowel is dead.

Pain characterization (OPQRST framework):

Associated symptoms that narrow the differential:

High-yield PMH cues:

Physical Exam Findings and Hemodynamic Assessment

— Hypotension + tachycardia + abdominal pain → suspect hemorrhage (ruptured AAA, ectopic, splenic), perforation with sepsis, or strangulated bowel

— Fever + tachycardia with localized peritonitis → intra-abdominal sepsis source control needed

— Narrow pulse pressure or shock index >1.0 → early hemorrhagic shock even with normal SBP

— Distension → obstruction, ascites, ileus

— Cullen sign (periumbilical ecchymosis) and Grey-Turner sign (flank ecchymosis) → retroperitoneal hemorrhage (hemorrhagic pancreatitis, ruptured AAA, ruptured ectopic)

— Surgical scars → adhesive obstruction risk

— Visible peristalsis → high-grade SBO

— High-pitched tinkling bowel sounds → early mechanical obstruction

— Absent bowel sounds → ileus or late peritonitis

— Bruits → vascular etiology

— Rigidity ("board-like abdomen") → perforated viscus with diffuse peritonitis

— Rebound tenderness, involuntary guarding → peritoneal inflammation

— Murphy sign: inspiratory arrest with RUQ palpation → acute cholecystitis (Sn ~65%)

— McBurney point tenderness, Rovsing, psoas, obturator signs → appendicitis

— Carnett sign: pain worse with tensed abdominal wall → abdominal wall etiology, not visceral

— Pulsatile expansile mass → AAA (palpation is ~50% sensitive, low specificity in obese)

— Rectal: gross or occult blood, mass, tenderness (retrocecal appendix), tone

— Pelvic in women: cervical motion tenderness (PID), adnexal mass (ectopic, torsion)

— Genital/groin: incarcerated hernia, testicular torsion masquerading as abdominal pain

— Hernia orifices: must palpate every patient with obstruction

Key distinction: Visceral pain is dull, poorly localized, midline. Parietal (somatic) pain is sharp, localized, worse with movement → indicates peritoneal irritation and is the threshold for surgical urgency.

Vitals-first approach:

Inspection:

Auscultation:

Percussion and palpation:

Mandatory adjunctive exams:

Diagnostic Workup — Initial Labs and Imaging

— CBC with differential (leukocytosis, left shift, anemia from bleed)

— BMP (electrolyte derangements from vomiting, AKI from hypoperfusion, anion gap)

— LFTs + lipase (biliary, pancreatitis)

— Lactate (ischemia, sepsis, hypoperfusion — >4 is ominous)

— Coags (PT/INR, PTT) — preoperative and if cirrhosis/anticoagulated

— Type and screen/crossmatch if bleeding or surgical candidate

— UA (hematuria → stone; pyuria → UTI/appendicitis adjacent; ketones → DKA)

— βhCG in every reproductive-age woman — before imaging

— Troponin + ECG in epigastric pain >40 yo (rule out inferior MI)

— VBG/ABG if shock or suspected ischemia

— Lipase preferred over amylase for pancreatitis (more specific, longer half-life)

— Upright CXR + upright/left lateral decubitus abdominal X-ray: free air under diaphragm (perforation), air-fluid levels (obstruction), pneumonia mimicking abdomen

— RUQ ultrasound: first-line for suspected cholecystitis/cholelithiasis (Sn ~90%) and for pregnant patients

— Transvaginal US: first-line for ectopic, ovarian torsion (with Doppler), TOA

— CT abdomen/pelvis with IV contrast: workhorse for undifferentiated acute abdomen — appendicitis, diverticulitis, SBO, perforation, abscess, ischemia

— CT angiography: mesenteric ischemia, AAA, GI bleed localization

— Bedside US (FAST): trauma or unstable patient — free fluid suggests hemoperitoneum

— Hemodynamically unstable patient with peritonitis → straight to OR

— Suspected ruptured AAA with hypotension → OR/endovascular suite, not CT first if unstable

CCS pearl: Order labs and imaging in parallel, not sequentially. On CCS, click CBC, BMP, lipase, lactate, βhCG, type and screen, upright CXR, and CT abdomen/pelvis with contrast in one batch — then move clock forward. Sequential ordering wastes simulated minutes.

Universal first-line labs:

Imaging — choosing wisely:

When NOT to delay surgery for imaging:

Diagnostic Workup — Advanced and Confirmatory Studies

— IV contrast: best for vascular, inflammatory, and ischemic processes

— Oral contrast: rarely needed acutely; can delay diagnosis

— Non-contrast CT: nephrolithiasis ("stone protocol"), contrast allergy, severe AKI

— Triple-phase CT: GI bleed, hepatic lesions, mesenteric ischemia (arterial + venous phases)

— MRCP for choledocholithiasis when US equivocal and LFTs suggest obstruction

— MRI abdomen for pregnant patients when US non-diagnostic (e.g., suspected appendicitis after equivocal US) — no ionizing radiation

— Confirms acute cholecystitis when US equivocal — non-visualization of gallbladder at 60 min = positive

— Useful in acalculous cholecystitis (critically ill, post-op, TPN patients)

— EGD: upper GI bleed, suspected perforated ulcer (after stabilization)

— Colonoscopy/flex sig: lower GI bleed source, ischemic colitis confirmation, sigmoid volvulus reduction

— ERCP: therapeutic for cholangitis (stone extraction, stent) and gallstone pancreatitis with persistent obstruction

— CT angiography first for mesenteric ischemia, AAA

— Conventional angiography therapeutic — embolization for GI bleed or visceral aneurysm rupture

— Mandatory in cirrhotic with ascites + abdominal pain or fever

— SBP = ascitic PMN ≥250/mm³ → empiric cefotaxime + albumin

— When imaging non-diagnostic but clinical suspicion remains high (especially young women with possible appendicitis vs. gyn pathology)

Board pearl: In a pregnant patient with suspected appendicitis, the sequence is: graded compression US first → if non-diagnostic, MRI without gadolinium → CT only as last resort. Appendicitis is the most common non-obstetric surgical emergency in pregnancy and presents in RUQ in the third trimester due to cecal displacement.

CT abdomen/pelvis nuances:

MRI/MRCP:

HIDA scan (cholescintigraphy):

Endoscopy:

Angiography:

Diagnostic paracentesis:

Diagnostic laparoscopy:

Risk Stratification and First-Line Management Logic

— Bucket 1 — Immediate OR: hemodynamic instability + peritonitis, ruptured AAA, perforated viscus with sepsis, strangulated bowel, ruptured ectopic with shock

— Bucket 2 — Urgent intervention within hours: appendicitis, cholecystitis, complicated diverticulitis, cholangitis (after biliary drainage), incarcerated hernia

— Bucket 3 — Admit, treat medically, reassess: uncomplicated diverticulitis, mild pancreatitis, SBP, partial SBO, ileus

— 2 large-bore IVs, isotonic crystalloid bolus (LR preferred over NS — avoids hyperchloremic acidosis)

— NPO

— NG tube if obstruction, ileus, or persistent vomiting

— Foley for strict I/O if unstable or going to OR

— Correct electrolytes (K+, Mg, Ca)

— Analgesia — opioids do NOT mask the diagnosis (debunked dogma; give morphine or fentanyl)

— Antiemetic (ondansetron)

— Empiric antibiotics if perforation, sepsis, cholangitis, complicated diverticulitis suspected — within 1 hour for septic patients

— Lactate, blood cultures × 2 before antibiotics

— Broad-spectrum antibiotics within 1 hour

— 30 mL/kg crystalloid for hypotension or lactate ≥4

— Vasopressors (norepinephrine) if MAP <65 after fluids

— Peritoneal signs of any kind

— Free air on imaging

— Failure to improve on medical therapy within 24–48 h

— Any obstruction with signs of strangulation (fever, leukocytosis, acidosis, focal tenderness)

Step 3 management: Don't withhold analgesia waiting for the surgeon — multiple RCTs show opioids do not impair diagnostic accuracy in acute abdomen. Adequate pain control is a quality measure and a Step 3 favorite.

The three-bucket triage:

Initial resuscitation bundle (every acute abdomen):

Sepsis bundle integration (Surviving Sepsis):

Surgical consultation triggers:

Pharmacotherapy — Empiric Regimens by Suspected Source

— Ceftriaxone 1–2 g IV + metronidazole 500 mg IV q8h (covers Gram-negatives + anaerobes)

— Alternative: ertapenem 1 g IV daily (single agent)

— Penicillin allergy: ciprofloxacin/levofloxacin + metronidazole

— Piperacillin-tazobactam 4.5 g IV q8h (broad coverage including Pseudomonas)

— Or meropenem 1 g IV q8h if ESBL risk

— Add vancomycin if MRSA risk (recent hospitalization, prior MRSA)

— Add fluconazole or echinocandin if Candida concern (perforated upper GI, immunosuppressed, recurrent)

— Pip-tazo or ceftriaxone + metronidazole

— Biliary drainage within 24–48 h via ERCP is the definitive therapy

— Cefotaxime 2 g IV q8h × 5 days + albumin 1.5 g/kg day 1, 1 g/kg day 3 (reduces hepatorenal syndrome)

— Secondary prophylaxis: ciprofloxacin 500 mg PO daily lifelong

— Aggressive IV LR (250–500 mL/h initially), pain control, early enteral nutrition within 24–72 h

— No prophylactic antibiotics in sterile necrosis — only if infected necrosis confirmed (gas on CT or positive aspirate) → carbapenem

— Recent guidelines (AGA) allow observation without antibiotics in select immunocompetent patients with mild disease

— If treating: amoxicillin-clavulanate or ciprofloxacin + metronidazole × 4–7 days

Board pearl: Prophylactic antibiotics in sterile pancreatic necrosis are NOT indicated — they don't reduce mortality and select for resistance/fungal infection. This reverses old teaching and is heavily tested.

Community-acquired intra-abdominal infection (mild-moderate):

High-risk or healthcare-associated intra-abdominal infection:

Cholangitis (Tokyo guidelines):

Spontaneous bacterial peritonitis:

Acute pancreatitis:

Diverticulitis (uncomplicated, outpatient):

Helicobacter-associated PUD: quadruple therapy (PPI + bismuth + tetracycline + metronidazole) after acute event resolved

Analgesia: fentanyl preferred in renal failure; avoid morphine in pancreatitis dogma is outdated — either acceptable

Procedures and Operative Management

— Laparoscopic appendectomy is standard

— Antibiotic-only therapy (ceftriaxone + metronidazole, then PO) is an option for uncomplicated appendicitis in selected adults — but ~40% recur within 5 years; counsel patients on shared decision

— Perforated with abscess: percutaneous drainage + antibiotics, interval appendectomy in 6–8 weeks (controversial)

— Early laparoscopic cholecystectomy within 72 hours of symptom onset (better outcomes than delayed)

— Critically ill/non-operative candidates: percutaneous cholecystostomy tube

— ERCP with sphincterotomy and stone extraction/stent placement is first-line drainage

— PTC if ERCP fails or anatomy precludes

— Cholecystectomy after recovery (during same admission for gallstone disease)

— Graham patch (omental patch) repair — laparoscopic or open

— H. pylori testing and eradication post-op

— Adhesive partial SBO: NG decompression, NPO, IV fluids, water-soluble contrast (Gastrografin) study — therapeutic and prognostic; surgery if no resolution in 48–72 h or signs of strangulation

— Complete SBO or closed-loop: urgent surgery

— Sigmoid volvulus: endoscopic detorsion + elective sigmoidectomy on same admission

— Cecal volvulus: surgical (right hemicolectomy)

— Embolic: catheter-directed thrombolysis or surgical embolectomy + bowel resection of necrotic segments

— Thrombotic: revascularization (bypass or stent)

— Non-occlusive: treat underlying low-flow state, papaverine infusion

— EVAR preferred over open repair when anatomy allows; massive transfusion protocol activated

CCS pearl: For surgical conditions, consult surgery early — even before all imaging returns. On CCS, "Consult General Surgery" should be clicked alongside the CT order, not after. Delays in consultation lower your score.

Appendicitis:

Cholecystitis:

Cholangitis:

Perforated peptic ulcer:

Bowel obstruction:

Mesenteric ischemia:

Ruptured AAA:

Special Populations — Elderly and Renal/Hepatic Impairment

— Atypical presentations are the rule: absent fever, blunted leukocytosis, minimal tenderness despite catastrophic pathology

— Mortality of acute abdomen in elderly: ~10× higher than younger adults

— Top diagnoses to actively exclude:

– Mesenteric ischemia (AFib, vascular disease) — lactate, CTA

– Ruptured AAA — bedside US, CTA

– Perforated diverticulitis (vs. uncomplicated in younger)

– Colon cancer with obstruction or perforation

– Sigmoid volvulus (chronic constipation, institutionalized)

– Acute cholecystitis with gangrene/emphysematous (diabetics)

— Lower threshold for CT imaging even with "soft" exam

— Medication review: anticoagulants (bleeding risk), NSAIDs (perforation), steroids (mask signs), metformin (hold before contrast if eGFR <30)

— Contrast considerations: current ACR guidance permits IV iodinated contrast in AKI/CKD when clinically necessary; benefit usually outweighs CIN risk

— eGFR <30 or dialysis: discuss with radiology; isosmolar contrast, minimize volume

— Drug dose adjustments: piperacillin-tazobactam, vancomycin, meropenem all renally dosed

— Avoid NSAIDs, morphine (active metabolites accumulate) — use fentanyl/hydromorphone

— Always tap the ascites to rule out SBP before treating abdominal pain as anything else

— Coagulopathy: vitamin K, FFP, or prothrombin complex for active bleeding or pre-procedure

— Avoid acetaminophen >2 g/day; avoid NSAIDs (renal + bleeding); reduce opioid doses

— Surgery risk stratification: MELD-Na and Child-Pugh classes predict perioperative mortality (MELD >15 = high risk)

Key distinction: In an elderly patient with new abdominal pain and AFib, mesenteric ischemia is the diagnosis to actively exclude — not appendicitis or diverticulitis. CTA is your test; delays directly correlate with mortality (>50% if >24 h).

Elderly patients (>65) — the high-stakes group:

Renal impairment:

Hepatic impairment / cirrhosis:

Special Populations — Pregnancy and Pediatrics

— βhCG positive: rule out ectopic first if <12 weeks (transvaginal US + quantitative βhCG; threshold for IUP ~1500–2000 mIU/mL)

— Appendicitis remains the most common non-obstetric surgical emergency — appendix migrates upward and laterally with gestation (RUQ in third trimester)

— Imaging hierarchy: US → MRI without gadolinium → CT if needed (don't withhold CT if life-threatening)

— Surgery in pregnancy: second trimester safest, but indicated emergency surgery should never be delayed regardless of trimester

— Avoid: NSAIDs (third trimester — ductus closure), tetracyclines, fluoroquinolones (relative), metronidazole (avoid first trimester if possible)

— Safe: penicillins, cephalosporins, acetaminophen, opioids (short-term)

— Placental abruption, uterine rupture, HELLP syndrome, ovarian vein thrombosis, ruptured corpus luteum, ovarian torsion (more common in pregnancy)

— Top diagnoses by age:

– <2 yrs: intussusception (currant jelly stool, sausage mass, target sign on US), malrotation with midgut volvulus (bilious emesis = emergency, upper GI series), pyloric stenosis (2–8 wks, projectile non-bilious)

– 2–5 yrs: intussusception, Meckel diverticulum bleed, HSP

– >5 yrs and adolescents: appendicitis (most common surgical cause), ovarian torsion, testicular torsion, ectopic in adolescents

— Bilious vomiting in a neonate = malrotation with volvulus until proven otherwise → emergent upper GI series → OR

— Intussusception: air or contrast enema is both diagnostic and therapeutic (success ~80%); surgery if failed or peritonitis

— Avoid CT when possible in children — use US first (especially for appendicitis — graded compression)

Board pearl: Bilious emesis in any infant <1 month is a surgical emergency — order an upper GI series stat and consult pediatric surgery. Missing midgut volvulus → bowel necrosis within hours.

Pregnancy — key principles:

Obstetric mimics of acute abdomen:

Pediatrics:

Complications and Adverse Outcomes

— Septic shock from perforation, cholangitis, or strangulated bowel — leading cause of mortality

— Hypovolemic/hemorrhagic shock from ruptured AAA, ectopic, splenic injury, GI bleed

— Bowel ischemia and necrosis from obstruction with strangulation, mesenteric ischemia, volvulus — requires resection; short bowel syndrome if extensive

— Multi-organ dysfunction: AKI (pre-renal + sepsis), ARDS (especially severe pancreatitis), DIC, hepatic dysfunction

— Abdominal compartment syndrome: intra-abdominal pressure >20 mmHg with organ dysfunction — measure bladder pressure; decompressive laparotomy if refractory

— Anastomotic leak (POD 5–7, fever, tachycardia, leukocytosis, peritonitis) — CT with rectal contrast, return to OR

— Surgical site infection — superficial vs. deep vs. organ-space (abscess)

— Postoperative ileus vs. early SBO — both present with distension and obstipation; CT distinguishes

— Wound dehiscence and evisceration — pink salmon-colored fluid from wound is pathognomonic warning

— Incisional hernia (long-term)

— Adhesions causing recurrent SBO (lifelong risk)

— DVT/PE — VTE prophylaxis (enoxaparin or heparin) within 24 h post-op unless contraindicated

— Post-ERCP pancreatitis (~5%) — rectal indomethacin reduces risk

— Severe pancreatitis: pseudocyst (>4 weeks), walled-off necrosis, pancreatic fistula, splenic vein thrombosis with gastric varices

— Cholangitis: hepatic abscess, recurrent strictures

— Complicated diverticulitis: abscess, fistula (colovesical — pneumaturia/fecaluria), stricture, perforation

— Mesenteric ischemia survivors: short gut, chronic mesenteric insufficiency

Step 3 management: POD 5–7 fever + tachycardia + leukocytosis after bowel surgery = anastomotic leak until proven otherwise. Order CT with water-soluble contrast (rectal or oral depending on anastomosis) and return to OR or IR drainage. Don't anchor on pneumonia or UTI.

Pre-treatment / disease-related complications:

Postoperative / procedural complications:

Disease-specific:

When to Escalate Care — ICU, Consult, and Triage

— Hemodynamic instability requiring vasopressors after adequate resuscitation

— Respiratory failure or impending intubation (ARDS, severe pancreatitis with abdominal compartment syndrome)

— Lactate >4 mmol/L not clearing with resuscitation

— Severe sepsis or septic shock

— Severe acute pancreatitis (BISAP ≥3, APACHE II ≥8, organ failure)

— Massive GI bleed with ongoing transfusion requirement

— Post-op patients after major emergency laparotomy, especially elderly or comorbid

— DKA or thyroid storm precipitated by intra-abdominal sepsis

— Persistent tachycardia, marginal blood pressure

— Cardiac comorbidities with abdominal sepsis

— Anticoagulation management needs

— General surgery: any peritonitis, free air, obstruction, ischemia, abscess >3–4 cm requiring drainage

— GI: GI bleed, suspected cholangitis (for ERCP), severe pancreatitis with biliary obstruction, IBD flare

— Interventional radiology: percutaneous abscess drainage, cholecystostomy, embolization for bleed, IVC filter, biliary drainage when ERCP not feasible

— Vascular surgery: AAA, mesenteric ischemia

— OB/Gyn: any reproductive-age woman with positive βhCG or adnexal findings

— Hepatology: decompensated cirrhosis with ascites, hepatorenal syndrome

— Need for services unavailable at current facility (e.g., vascular surgery, interventional radiology, NICU/PICU)

— Pediatric patients without pediatric surgical capability

— Hemodynamically stable patients only — stabilize first, never transfer crashing patient without damage-control surgery if possible

CCS pearl: On a 5-day CCS case, move the patient to the appropriate location early — ED → OR → SICU → floor → discharge. Each location change should be deliberate and timed with clinical milestones (extubation, off pressors, tolerating diet).

ICU admission criteria for acute abdomen:

Step-down/telemetry indications:

Consultation triggers:

Transfer criteria:

Key Differentials — Same-Category (Intra-Abdominal) Causes

— RUQ: cholecystitis, cholangitis, choledocholithiasis, hepatitis, hepatic abscess, Fitz-Hugh-Curtis (perihepatitis from PID), Budd-Chiari, duodenal ulcer, retrocecal appendicitis

— Epigastric: PUD, perforated ulcer, pancreatitis, gastritis, GERD, MI (mimic), AAA

— LUQ: splenic infarct/rupture/abscess, gastric ulcer, gastric volvulus, pancreatitis (body/tail), splenic flexure ischemia

— RLQ: appendicitis, cecal volvulus, Crohn ileitis, mesenteric adenitis, Meckel diverticulitis, ovarian torsion, ectopic, TOA, ureteral stone, inguinal hernia, psoas abscess

— LLQ: diverticulitis, sigmoid volvulus, ischemic colitis (watershed at splenic flexure and rectosigmoid), ovarian torsion, ectopic, ureteral stone

— Diffuse: peritonitis from any perforation, mesenteric ischemia, SBO/LBO, gastroenteritis, DKA, sickle cell crisis

— Appendicitis vs. ovarian torsion vs. ectopic vs. PID: all RLQ pain in young women — βhCG and pelvic US are non-negotiable

— Cholecystitis vs. cholangitis vs. choledocholithiasis: fever + jaundice differentiates cholangitis; biliary colic resolves <6 h, cholecystitis persists, cholangitis adds fever ± shock

— Diverticulitis vs. colon cancer perforation: elderly with new perforation — must scope after recovery (~6 weeks) to exclude malignancy

— Pancreatitis vs. perforated ulcer: both epigastric, both elevate amylase/lipase modestly — upright CXR for free air; CT clarifies

— SBO vs. ileus vs. pseudo-obstruction (Ogilvie): Ogilvie has massive colonic dilation without mechanical lesion — neostigmine if cecum >12 cm

— Ruptured AAA presenting as "renal colic" in elderly male — classic missed diagnosis

— Mesenteric ischemia presenting as "gastroenteritis" — pain out of proportion is the tell

Key distinction: Charcot triad (RUQ pain + fever + jaundice) = cholangitis; add hypotension + altered mental status = Reynolds pentad = suppurative cholangitis → emergent biliary drainage.

By quadrant — high-yield mapping:

Critical mimics that share features:

Vascular catastrophes in disguise:

Key Differentials — Extra-Abdominal and Medical Causes

— Inferior MI: epigastric pain, nausea, diaphoresis — always ECG in patients >40 with epigastric pain

— Pericarditis, myocarditis: can refer to epigastrium

— Lower lobe pneumonia: referred upper abdominal pain, especially in children

— Pulmonary embolism: pleuritic referred pain, dyspnea

— Aortic dissection: tearing pain radiating to back/abdomen

— DKA: abdominal pain in 30% — check anion gap and glucose in all undifferentiated abdominal pain

— Adrenal crisis: abdominal pain, hypotension, hyponatremia, hyperkalemia

— Hypercalcemia: "stones, bones, abdominal groans, psychiatric moans"

— Thyroid storm: abdominal pain, vomiting, tachycardia, fever

— Acute intermittent porphyria: young woman, recurrent severe abdominal pain, neurologic symptoms, dark urine, hyponatremia

— Sickle cell vasoocclusive crisis with splenic/hepatic sequestration

— Hereditary spherocytosis with splenic infarct

— HSP with intussusception risk in children

— Lead poisoning: "lead colic" — basophilic stippling, microcytic anemia, occupational exposure

— Black widow envenomation: abdominal rigidity mimicking peritonitis

— Cocaine, methamphetamine: mesenteric vasospasm, ischemia

— Opioid withdrawal: cramping, diarrhea

— ACE inhibitor angioedema of bowel: recurrent unexplained abdominal pain on lisinopril

— Familial Mediterranean fever: recurrent self-limited polyserositis in patients of Mediterranean descent — colchicine prophylaxis

— Herpes zoster: unilateral dermatomal pain before rash appears

— C. difficile colitis: post-antibiotic abdominal pain, diarrhea, leukocytosis (can be >30k); toxic megacolon risk

— Tuberculous peritonitis in immigrants, HIV

— IBS, functional dyspepsia — diagnosis of exclusion in acute setting

Board pearl: Always check an ECG and glucose in a patient with epigastric pain — missed inferior MI and DKA are classic Step 3 pitfalls. A normal lipase doesn't rule out either.

Cardiopulmonary mimics:

Endocrine/metabolic:

Hematologic:

Toxic/drug-related:

Infectious / autoimmune:

Functional:

Secondary Prevention / Discharge Medications / Long-Term Plan

— Post-appendectomy: wound care, return precautions, no antibiotics needed if uncomplicated; activity restrictions 1–2 weeks

— Post-cholecystectomy: low-fat diet initially; postcholecystectomy syndrome workup if persistent symptoms (MRCP for retained stone); 5–10% develop diarrhea (cholestyramine helps)

— Diverticulitis recovery: high-fiber diet, hydration; colonoscopy 6–8 weeks post-resolution in patients without recent screening to exclude malignancy (especially complicated diverticulitis); discuss elective sigmoidectomy after recurrent episodes or complicated disease

— Peptic ulcer: test and treat H. pylori (urea breath test or stool antigen 4 weeks after PPI stopped); PPI continued 8 weeks; avoid NSAIDs or add PPI prophylaxis if NSAID required; smoking cessation

— Pancreatitis (gallstone): cholecystectomy during same admission (or within 2 weeks) — reduces recurrence by 80%

— Pancreatitis (alcohol): alcohol cessation counseling, naltrexone or acamprosate, AA referral

— SBP survivors: lifelong ciprofloxacin or TMP-SMX prophylaxis; evaluate for liver transplant

— AAA repair: surveillance imaging (CT at 1 month, then yearly), aggressive CV risk reduction (statin, BP control, smoking cessation, antiplatelet)

— Mesenteric ischemia survivors: anticoagulation if embolic source; antiplatelet + statin if atherosclerotic; nutritional support

— Adhesive SBO managed non-operatively: dietary counseling, recognize early recurrence symptoms; recurrence rate ~30%

— VTE prophylaxis duration: extended (28 days) after major abdominal cancer surgery; standard post-op for benign cases

— Pain control: opioid stewardship — limit quantity, multimodal (acetaminophen + NSAID if appropriate + topical), naloxone co-prescription for high-risk

— Vaccination updates if splenectomy: pneumococcal (PCV20 or PCV15+PPSV23), meningococcal (ACWY + B), Hib; lifelong daily penicillin in children

— Smoking cessation, alcohol counseling, weight management

Step 3 management: After gallstone pancreatitis, do cholecystectomy during the same admission once the patient is clinically improving — discharge without cholecystectomy is a quality-measure failure and predicts 30% recurrence within weeks.

Discharge planning by condition:

Universal post-acute-abdomen:

Follow-Up, Monitoring, and Counseling

— PCP follow-up within 7–14 days post-discharge for any acute abdomen admission

— Surgery follow-up at 2–4 weeks post-operatively (wound check, staple/suture removal, pathology review)

— Earlier follow-up (3–5 days) if elderly, complicated course, new anticoagulation, or wound concerns

— Diverticulitis: colonoscopy 6–8 weeks post-resolution if not recent; repeat screening interval per pathology

— Colon cancer found at surgery: oncology referral, CEA baseline and q3–6 months × 2 years, then q6 months × 3 years; surveillance colonoscopy at 1 year, then 3 years, then 5 years

— Cholecystectomy with retained stone risk: LFTs at 2 weeks; MRCP if abnormal

— Pancreatitis: lipid panel, calcium, IgG4 to identify etiology; repeat imaging at 4–6 weeks if necrosis or pseudocyst

— AAA repair: CT at 1 month, 6 months, 12 months, then annually; lifelong surveillance for endoleak after EVAR

— IBD-related surgery: GI follow-up, restart maintenance therapy

— Return precautions: fever >38.5, worsening pain, vomiting, inability to tolerate PO, wound erythema/discharge, syncope, melena

— Activity progression: no heavy lifting (>10 lb) for 4–6 weeks after open laparotomy; less restriction after laparoscopy

— Sexual activity, driving (off opioids and able to brake firmly), return to work — usually 1–2 weeks for laparoscopic, 4–6 for open

— Diet progression: clear → full → regular as tolerated; specific restrictions only when indicated (e.g., low-fat post-cholecystectomy initially)

— Smoking cessation (improves wound healing, reduces VTE) and alcohol moderation

— VTE awareness: leg swelling, calf pain, dyspnea

Board pearl: After complicated diverticulitis, colonoscopy in 6–8 weeks is mandatory to rule out underlying colorectal cancer — perforation in elderly can be the presenting feature of malignancy. Skipping this is a frequent question stem trap.

Standard post-discharge cadence:

Condition-specific monitoring:

Counseling priorities:

Vaccinations and chronic disease optimization: diabetes control, statin initiation per ASCVD risk, hypertension management — abdominal admission is a teachable moment

Ethical, Legal, and Patient Safety Considerations

— Standard consent requires disclosure of diagnosis, proposed procedure, risks/benefits, alternatives, risks of no treatment

— Emergency exception ("implied consent"): when patient lacks capacity and delay would cause death or serious harm, consent is implied for life-saving surgery — but document the emergency and attempt to reach surrogate

— Capacity assessment: even acutely ill patients may retain capacity; pain and opioids don't automatically remove it

— Jehovah's Witness patients refusing blood: respect competent refusal in adults; bloodless protocols available; in pediatrics, court order may be sought for life-threatening situations

— Universal Protocol/Time-out before any procedure: correct patient, site, procedure

— Wrong-site surgery prevention: site marking by surgeon with patient awake when possible

— Surgical safety checklist (WHO) reduces mortality

— VTE prophylaxis is a CMS quality measure — document if held

— Glycemic control perioperatively (target 140–180); avoid sliding scale alone in inpatients

— Antibiotic timing: prophylactic dose within 60 minutes of incision (120 min for vancomycin/fluoroquinolones)

— Handoffs (ED → OR → ICU → floor): use structured tools (SBAR, I-PASS); transitions are the highest-risk moments for error

— Suspected non-accidental trauma in pediatric acute abdomen (duodenal hematoma, mesenteric injury) — report to CPS

— Elder abuse (unexplained injuries, neglect) — adult protective services

— Penetrating injuries — many states require gunshot/stab reporting to law enforcement

— Ethical and increasingly legally required — disclose unanticipated outcomes honestly; apology laws in many states protect from admissibility

Step 3 management: A patient on warfarin with INR 4.5 arriving with perforated diverticulitis needs emergent surgery — give 4-factor PCC + IV vitamin K for rapid reversal; do not wait for FFP alone. Document the urgency, obtain consent or invoke emergency exception, and proceed. This vignette tests reversal AND ethics simultaneously.

Informed consent in emergency surgery:

Surrogate decision-making hierarchy (varies by state but typically): spouse → adult children → parents → siblings → other relatives → close friend; document advance directives, POLST/MOLST

Patient safety in acute abdomen care:

Mandatory reporting situations:

Disclosure of medical errors:

High-Yield Associations and Rapid-Fire Clinical Facts

— Murphy sign — cholecystitis

— McBurney point, Rovsing, psoas, obturator signs — appendicitis

— Cullen / Grey-Turner — retroperitoneal hemorrhage

— Kehr sign (left shoulder pain) — splenic rupture (phrenic referral)

— Charcot triad / Reynolds pentad — cholangitis

— Carnett sign — abdominal wall pain

— Fothergill sign — rectus sheath hematoma

— Sister Mary Joseph nodule — umbilical metastasis (gastric, ovarian)

— Cope obturator/psoas — pelvic/retroperitoneal inflammation

— Free air under diaphragm — perforated viscus

— Coffee bean / bent inner tube sign — sigmoid volvulus

— Bird's beak on contrast enema — volvulus

— Target / pseudokidney sign — intussusception

— String sign — Crohn ileitis; also pyloric stenosis

— Apple core lesion — colon cancer

— Thumbprinting — ischemic colitis

— Pneumatosis intestinalis + portal venous gas — bowel ischemia (late, ominous)

— Whirl sign — volvulus or internal hernia on CT

— Lipase >3× ULN — pancreatitis

— ALT/AST >1000 — shock liver or viral; cholangitis rarely this high

— Lactate >4 with abdominal pain — ischemia or sepsis until proven otherwise

— WBC >20k with abdominal pain — think C. diff, abscess, ischemia

— Disproportionate leukocytosis with bandemia + abdominal pain in elderly — mesenteric ischemia

— NSAIDs → PUD, perforation, ischemic colitis

— OCPs → mesenteric vein thrombosis, hepatic adenoma rupture

— Cocaine → mesenteric ischemia

— Anticoagulants → rectus sheath hematoma, retroperitoneal bleed

— ACEi → bowel angioedema

— Opioids → constipation, Ogilvie

— Appendicitis lifetime risk: 7%

— AAA screening: men 65–75 who ever smoked — one-time US (USPSTF)

— Gallstone pancreatitis recurrence without cholecystectomy: ~30% within weeks

Board pearl: Pneumobilia + small bowel obstruction + ectopic gallstone on imaging = gallstone ileus (Rigler triad) — usually elderly woman, stone erodes into duodenum (cholecystoduodenal fistula) and lodges at ileocecal valve.

Eponyms and signs:

Classic imaging findings:

Lab tells:

Drug-disease associations:

Rule-of-thumb numbers:

Board Question Stem Patterns

— Stem: 78 yo with AFib not on anticoagulation, sudden severe periumbilical pain, soft abdomen, lactate 6

— Answer: CT angiography → acute mesenteric ischemia → embolectomy/revascularization

— Stem: 70 yo male smoker, sudden flank/back pain, hypotensive, pulsatile mass

— Answer: Ruptured AAA → OR/endovascular immediately; do not delay for CT if unstable

— Stem: 24 yo woman, RLQ pain, LMP 7 weeks ago

— First step: βhCG → if positive, transvaginal US for ectopic

— Stem: POD 6 after sigmoidectomy, fever 39, tachycardia, abdominal pain, leukocytosis

— Answer: Anastomotic leak → CT with contrast → IR drainage or OR

— Stem: cirrhotic with ascites, mild diffuse pain, low-grade fever

— Answer: Diagnostic paracentesis → if PMN ≥250, treat as SBP with cefotaxime + albumin

— Stem: 3-week-old infant, bilious emesis, irritable

— Answer: Upper GI series → malrotation with midgut volvulus → emergent Ladd procedure

— Stem: 60 yo on naproxen for OA, sudden severe epigastric pain, rigid abdomen, free air on CXR

— Answer: Perforated peptic ulcer → resuscitation, antibiotics, Graham patch repair

— Stem: Charcot triad, then hypotension and confusion

— Answer: Suppurative cholangitis → antibiotics + emergent ERCP

— Stem: 60 yo after first episode of complicated diverticulitis, resolved

— Answer: Colonoscopy in 6–8 weeks to exclude malignancy

— Stem: 3rd trimester, RUQ pain, fever, leukocytosis

— Answer: Appendicitis (appendix migrates) → graded US, then MRI; appendectomy regardless of trimester

CCS pearl: Recognize the stem within 2 sentences, then commit to the diagnostic + therapeutic cascade. Wrong answer choices are usually "next-best" tests that delay definitive action — pick the action, not the additional test, when the diagnosis is clear.

Pattern 1 — Elderly with AFib and "out of proportion" pain:

Pattern 2 — Hypotensive elderly male with back pain:

Pattern 3 — Reproductive-age woman with RLQ pain:

Pattern 4 — POD 5 fever after colectomy:

Pattern 5 — Cirrhotic with new abdominal pain:

Pattern 6 — Neonate with bilious vomiting:

Pattern 7 — Epigastric pain in patient on NSAIDs:

Pattern 8 — RUQ pain with jaundice and fever:

Pattern 9 — Diverticulitis follow-up:

Pattern 10 — Pregnant with RUQ pain:

One-Line Recap

Acute abdomen is a triage problem: resuscitate, identify the surgical and life-threatening causes (perforation, ischemia, hemorrhage, strangulation) before everything else, and use focused history, exam, and CT/US to decide OR vs. IR vs. medical management within the first hour.

Board pearl: When the stem gives you a vascular comorbidity (AFib, smoking, atherosclerosis) plus abdominal pain that doesn't match the exam, the answer is almost always a vascular catastrophe — CT angiography is your friend, and time-to-diagnosis directly drives mortality.

The non-negotiable opening orders: 2 large-bore IVs, NPO, LR, CBC/BMP/lipase/lactate/coags/type and screen, βhCG in every reproductive-age woman, upright CXR, ECG if epigastric pain, and CT abdomen/pelvis with IV contrast — ordered in parallel, not sequence

The five "can't-miss" diagnoses: ruptured AAA, mesenteric ischemia, perforated viscus, ruptured ectopic, strangulated bowel — each has a demographic anchor (elderly smoker, AFib, NSAID user, reproductive-age woman, prior surgery) that should trigger active exclusion

The decision rule: peritonitis or hemodynamic instability with a surgical abdomen → OR now; stable with imaging-confirmed infection → antibiotics + targeted intervention (ERCP, drainage, delayed surgery); equivocal → admit, serial exams, repeat imaging, surgical consult on board

The Step 3 finishing touches: cholecystectomy same admission for gallstone pancreatitis, colonoscopy in 6–8 weeks after complicated diverticulitis, H. pylori test-and-treat after perforated ulcer, SBP prophylaxis lifelong after first episode, VTE prophylaxis within 24 h post-op, and a structured handoff at every transition of care