Acute abdomen

Last updated: May 12, 2025

Quick guide

Diagnostic approach

ABCDE approach
Focused clinical evaluation
CBC
CMP
Troponin
Lipase, amylase
Lactate
Coagulation panel
Type and screen
Urine β-hCG in individuals who can become pregnant
UA
Cultures (e.g., blood, urine)
12-lead ECG
Ultrasound (e.g., biliary, renal, pelvic, testicular, AAA) based on clinical suspicion
CT abdomen

Management checklist

IV access
NPO
IV fluid resuscitation as needed
Parenteral analgesics
Empiric antibiotics for intraabdominal infections as indicated
Antiemetics
NG tube placement as needed
Urinary catheter placement (e.g., Foley catheter) as needed
Specialty consult based on suspected etiology

Red flag features

Age > 50 years
Immunocompromise
Previous abdominal surgery
History of CAD and/or atrial fibrillation
Unstable vital signs
Sudden onset of severe pain
Pain that interrupts sleep
Pain out of proportion to abdominal findings
Bilious vomiting
Hematemesis, hematochezia
Jaundice
Peritoneal signs
Absent or tinkling bowel sounds
Gross abdominal distention
Irreducible, tender bulge on abdomen or groin

Life-threatening causes

Summary

Acute abdomen refers to severe abdominal pain lasting for hours to a few days. The underlying pathology may be intraabdominal, thoracic, or systemic and may require urgent surgical intervention. The initial approach to acute abdomen should be to assess for immediately life-threatening causes (e.g., ruptured abdominal aortic aneurysm, bowel perforation) by checking vital signs, performing a quick physical examination, and immediately conducting the appropriate focused diagnostic tests (e.g., abdominal ultrasound, abdominal x-ray). Once emergency causes have been ruled out, a thorough history and physical examination should be performed to narrow the differential diagnoses and guide further diagnostic workup and therapy. Causes of chronic abdominal pain are not addressed in this article.

See “Blunt abdominal trauma” and “Penetrating abdominal trauma” for details on traumatic causes of abdominal pain.

Recognizing an acute abdomen

Initial management

Approach ^[1]

Evaluate and stabilize critically ill patients concurrently.

Perform ABCDE survey: e.g., large-bore IV access, fluid resuscitation, crossmatch and emergency transfusion for suspected hemorrhagic shock.
Establish NPO status.
Perform a focused clinical evaluation, including pelvic, testicular, and rectal examination, if indicated.
Perform targeted diagnostic workup of acute abdomen.
Obtain urgent specialty consult as needed, e.g., general surgery, vascular surgery, urology, OB/GYN (see “Disposition” for details).
Administer supportive care for acute abdominal pain as needed.
Identify and treat the underlying cause.

Remember to consider gynecological causes such as PID and pregnancy-related conditions. ^[2]

Red flags for abdominal pain

The following red flags highlight conditions that can put patients at high risk for life-threatening causes of abdominal pain or misdiagnosis.

Risk factors
- Age > 50 years
- Immunocompromise ^[3]
- Previous abdominal surgery ^[4]
- History of CAD and/or atrial fibrillation
Unstable vital signs: hypotension, tachycardia
Pain characteristics
- Sudden onset of severe pain
- Pain that interrupts sleep
- Pain out of proportion to abdominal findings
Accompanying symptoms
Findings on examination
- Possible peritoneal signs
  - Guarding and/or rigidity (focal or diffused)
  - Rebound tenderness (focal or diffused)
- Absent or tinkling bowel sounds
- Gross abdominal distention
- Irreducible, tender bulge on abdomen or groin

Abdominal pain accompanied by hemodynamic instability may indicate internal bleeding, perforated viscus, necrotic bowel, or sepsis.

Maintain a high index of suspicion in immunocompromised and older patients, as they may present without fever, leukocytosis, or localized abdominal tenderness despite having an underlying life-threatening disease. ^[3]^[5]

Immediately life-threatening diagnoses

Delays in treatment of serious intraabdominal causes of acute abdominal pain can result in bowel necrosis, sepsis, fistula formation, and death.

Disposition ^[6]^[7]

Hemodynamically unstable patients: Consider direct transfer to OR for patients needing emergency surgery or ICU admission.
Underlying surgical pathology, intractable nausea and vomiting, and/or unremitting pain: inpatient admission
Stable patients with inconclusive or negative diagnostic workup
- Extended observation in the ED with serial abdominal examination
- OR consider discharge with instructions and follow-up if the following criteria are met: :
  - Resolution of pain and nausea
  - Ability to tolerate oral intake
  - Reassuring general appearance and physical examination
  - Ability to adhere to discharge instructions.
Examples of urgent consultations
- Vascular surgery for a ruptured or symptomatic AAA
- General surgery for hemodynamically unstable patients with a rigid abdomen
- Urology for testicular torsion
- OB/GYN for a ruptured ectopic pregnancy

Diagnostics

The diagnostic workup should be guided by the pretest probability of the diagnoses under consideration. The following list includes some commonly used diagnostic tools that can help to diagnose or rule out possible etiologies in a patient with acute abdominal pain.

Laboratory studies

Blood gas analysis
Lactate
Troponin
Serum glucose
CBC
Coagulation studies (e.g., INR, PT)
BMP
LFTs
Lipase, amylase
Blood type and screen
ESR/CRP
Urinalysis
β-hCG urine test
Cultures

Strongly consider a urine pregnancy test in sexually active female patients of reproductive age, irrespective of current contraception use.

Patients with obvious signs of diffuse peritonitis or sepsis may require immediate surgical management without further diagnostic imaging.

Imaging ^[8]^[9]^[10]^[11]^[12]^[13]^[14]

Approach

The initial imaging modality should be guided by the working diagnosis, as based on the patient history, vital signs, and examination.
The following recommendations apply to nonpregnant adults.
In pregnant women with acute abdominal pain, ultrasound and/or MRI of the abdomen and/or pelvis without contrast are the preferred initial imaging modalities.

By suspected diagnosis ^[11]

Suspected diagnosis	Recommended imaging modality
Acute coronary syndrome	ECG TTE
Hemorrhagic shock ^[12]	FAST
Bowel perforation ^[8]	CT abdomen and pelvis with IV contrast X-ray abdomen (upright and supine) with x-ray chest (upright)
Small bowel obstruction ^[9]
Intraabdominal abscess	CT abdomen and pelvis with IV contrast
Acute diverticulitis ^[13]
Acute appendicitis ^[10]
Acute mesenteric ischemia ^[15]	CTA of the abdomen
Acute pancreatitis ^[16]	Ultrasound abdomen CT abdomen with IV contrast
Nephrolithiasis ^[17]	Ultrasound abdomen and pelvis CT abdomen and pelvis without contrast ^[17]^[18]^[19]
Acute complicated pyelonephritis ^[12]	CT abdomen and pelvis with IV contrast
Suspected symptomatic AAA in a hemodynamically stable patient ^[20]	Ultrasound abdomen CT/MR angiography

By location of the pain

Site of pain
Site of pain	Initial test of choice	Alternatives
RUQ pain ^[21]	Ultrasound abdomen	CT abdomen with IV contrast MRCP Acalculous cholecystitis suspected: HIDA scan
RLQ pain ^[10] or LLQ pain ^[13]	CT abdomen and pelvis with IV contrast	CT abdomen and pelvis without IV contrast MRI abdomen and pelvis with or without IV contrast Abdominal and/or pelvic ultrasound Suspected ovarian/testicular torsion: duplex ultrasound of the pelvis (♀)/scrotum (♂)
LUQ pain ^[22]	CT abdomen with oral and IV contrast	Acute abdominal series
Suprapubic pain ^[22]	Ultrasound abdomen and pelvis	CT abdomen and pelvis with/without IV contrast MRI with/without IV contrast Transvaginal ultrasound
Pelvic pain	See “Diagnostic workup of pelvic pain.”
Nonlocalized pain ^[8]	CT abdomen and pelvis with IV contrast	CT abdomen and pelvis without IV contrast MRI abdomen and pelvis with/without IV contrast Ultrasound abdomen and/or pelvis Postoperative patients with acute abdomen: Consider fluoroscopy (enema and/or upper abdominal series).

Abdominal quadrants Abdominal regions

Maintain a low threshold for obtaining diagnostic imaging in older patients, for whom abdominal pain is associated with higher morbidity and mortality as well as lower initial diagnostic accuracy. ^[23]

Consider diagnostic laparoscopy in hemodynamically stable patients in which the diagnosis is still unclear after complete physical examination and imaging. For patients with hemodynamic instability or severe abdominal distention, proceed to diagnostic laparotomy. ^[24]

In pregnant patients, regardless of the site of pain, ultrasound and MRI are the preferred initial imaging modalities.

Cardiovascular causes

Cardiovascular causes of acute abdominal pain
	Clinical features	Diagnostic findings	Acute management
Acute coronary syndrome ^[25]^[26]	Heavy, dull, pressure/squeezing sensation Substernal or epigastric pain with radiation to left shoulder Nausea, vomiting Diaphoresis, anxiety Dizziness, lightheadedness, syncope Pain may improve with nitroglycerin.	ECG: nonspecific changes, ST-segment elevation/depression, T-wave inversions, Q waves Increased or normal troponin TTE: hypokinesis, regional wall motion abnormalities	See the “Acute management checklist for STEMI” and “Acute management checklist for NSTEMI/UA.”
Acute mesenteric ischemia ^[27]^[28]^[29]^[30]	Age > 60 years, embolic risk factors (e.g., atrial fibrillation, thrombophilia), cardiovascular disease Pain out of proportion to findings Severe, diffuse abdominal pain and distention Vomiting, diarrhea Melena, hematochezia	Labs: lactic acidosis, hyperkalemia, leukocytosis X-ray abdomen: normal (early stages), pneumatosis intestinalis (late stages) CT angiography: mesenteric arterial narrowing or occlusion, thickening of bowel wall, nonenhancing segments of solid organs or of the bowel wall, pneumatosis intestinalis	See the “Acute management checklist for acute mesenteric ischemia.”
Ruptured AAA (or impending rupture) ^[31]	Age > 50 years Sudden, severe central abdominal, chest, and/or back pain Hypotension, shock Pulsatile mass in the midline of the abdomen Grey Turner sign and/or Cullen sign History of atherosclerosis, hypertension, and/or smoking	Imaging is only recommended in hemodynamically-stable patients with a low pretest probability of ruptured AAA. Abdominal ultrasound: aortic dilatation, periaortic fluid, intraperitoneal free fluid (See also “POCUS for suspected AAA.”) CT/MR angiography: retro- and intraperitoneal hemorrhage; localization of the ruptured/leaking site	See the “Acute management checklist for ruptured AAA.”
Aortic dissection ^[32]^[33]^[34]	Sudden onset of severe, sharp tearing chest or abdominal pain that radiates to the back Hypotension, syncope, neurological symptoms Asymmetrical blood pressure, pulse deficit New diastolic murmur (due to aortic regurgitation) Symptoms of myocardial ischemia	Elevated D-dimer ECG: nonspecific ST-segment changes CXR: widening of the aorta CT angiography of chest/abdomen/pelvis: intimal flap with false lumen Transesophageal echocardiography (TEE): proximal aortic dissection, tamponade, aortic regurgitation	See the “Acute management checklist for aortic dissection.”

POCUS (abdomen): aortic aneurysm POCUS (abdomen): free fluid in hepatorenal recess (Morison pouch) Classifications of aortic dissection Widened mediastinum

Gastrointestinal causes

Gastrointestinal causes of acute abdomen
	Clinical features	Diagnostic findings	Acute management
GI tract perforation ^[8]^[35]^[36]	Sudden onset of diffuse abdominal pain Nausea, vomiting Constipation/obstipation Diffuse abdominal guarding, rigidity, and rebound tenderness Absent bowel sounds Loss of liver dullness on RUQ percussion	Abdominal x-ray: pneumoperitoneum	See the “Acute management checklist for GI tract perforation” and “Acute management checklist for esophageal perforation.”
Mechanical bowel obstruction ^[8]^[9]^[37]^[38]	Colicky abdominal pain Obstipation/bloating Progressive nausea and vomiting (late finding) Diffuse abdominal distention, tympanic abdomen, collapsed rectum on DRE Tinkling bowel sounds History of abdominal surgery	X-ray abdomen Dilated bowel loops proximal to the obstruction Rectal air shadow absent Multiple air-fluid levels CT abdomen with IV contrast Similar findings as on x-ray Transition point at site of obstruction	See the “Acute management checklist for mechanical bowel obstruction.”
Acute appendicitis (including perforated appendicitis) ^[39]^[40]^[41]^[42]	RLQ, epigastric, and/or periumbilical pain (migrating abdominal pain) Fever Nausea, anorexia Guarding, tenderness, and rebound tenderness in the RLQ	Neutrophilic leukocytosis Abdominal CT scan with IV contrast : distended appendix with periappendiceal fat stranding Abdominal ultrasonography : noncompressible, aperistaltic, distended appendix, probe tenderness in the RLQ, Target sign	See the “Acute management checklist for acute appendicitis.”
Peptic ulcer disease ^[43]^[44]^[45]	Epigastric pain Duodenal ulcer: pain relieved with food; weight gain Gastric ulcer: pain exacerbated by food; weight loss Signs of GI bleed History of NSAID intake	Anemia, positive FOBT (in cases of bleeding ulcer) Urea breath test for H. pylori: positive in most cases of PUD EGD: Mucosal erosions and/or ulcers are required for a definitive diagnosis.	See the “Acute management checklist for peptic ulcer disease.”
Diverticulitis ^[46]^[47]^[48]^[49]^[50]^[51]^[52]	Fever LLQ pain Constipation Tender mass in LLQ	Labs: ↑ WBC CT abdomen and pelvis with IV contrast: colonic diverticula with pericolic mesenteric fat stranding	See the “Acute management checklist for diverticulitis.”
Gastroenteritis ^[53]	Abdominal cramping Diarrhea, nausea, and/or vomiting Mild cases: normal abdominal examination Severe cases: abdominal tenderness, fever, dehydration	Diagnostic studies typically not required CBC and BMP can be considered for severe gastroenteritis or in patients with risk factors for severe illness	See the “Acute management checklist for infectious gastroenteritis.”
Neutropenic enterocolitis (typhlitis) ^[54]^[55]^[56]	Fever Bloody diarrhea RLQ pain Presence of oral or anal mucosal inflammation. ^[57]	Laboratory studies: neutropenia CT abdomen and pelvis with IV contrast Cecal distention Cecal wall thickening Pneumatosis intestinalis Mesenteric stranding Pericolic fluid Abdominal ultrasonography ^[58] Findings similar to CT scan Absent peristalsis	Empiric broad-spectrum antibiotics Bowel rest IV fluid therapy Consult surgery if there are signs of: Bowel perforation Persistent GI bleeding Clinical deterioration with medical management alone See also “Management of neutropenic fever.”
Epiploic appendagitis ^[59]^[60]	Lower abdominal pain	Laboratory studies: typically normal CT abdomen and pelvis with IV contrast Ovoid lesion of fat density with high-density rim adjacent to the colon Localized fat stranding	Self-limited; can be treated with NSAIDs

Biliary and pancreatic causes

Biliary and pancreatic causes of acute abdomen
	Clinical features	Diagnostic findings	Acute management
Acute pancreatitis ^[61]^[62]^[63]	Severe epigastric pain that radiates to the back (circumferential pain) Nausea, vomiting Epigastric tenderness, guarding, rigidity Hypoactive bowel sounds Possibly fever History of gallstones or alcohol use	↑ Lipase, amylase Hypocalcemia (poor prognostic indicator) Abdominal ultrasound: pancreatic edema, peripancreatic fluid, gallstones Abdominal CT with IV contrast : pancreatic edema, peripancreatic fat stranding, gallstones	See the “Acute management checklist for acute pancreatitis.”
Symptomatic cholelithiasis ^[64]^[65]^[66]	Biliary colic: RUQ pain with radiation to the right shoulder Postprandial onset Nausea, vomiting Normal abdominal examination	Labs: normal Abdominal ultrasound: gallstones with posterior acoustic shadow See also “POCUS for cholelithiasis.”	See the “Acute management checklist for biliary colic.”
Choledocholithiasis ^[64]^[67]	RUQ pain Features of obstructive jaundice Nausea, vomiting Normal abdominal examination	Labs: ↑ ALP, AST, ALT, total bilirubin Abdominal ultrasound ^[68]^[69] Dilated common bile duct (CBD) Intrahepatic biliary dilatation Echogenic structure within the CBD with shadowing EUS: stone within the CBD MRCP or ERCP: filling defect in the contrast-enhanced duct	See the “Acute management checklist for choledocholithiasis.”
Acute cholecystitis ^[64]^[65]^[70]^[71]^[72]	Severe RUQ pain Fever, chills Nausea, vomiting Right shoulder referred pain Murphy sign	Labs: ↑ WBC Abdominal ultrasound (see also “Biliary POCUS”): sonographic Murphy sign , pericholecystic fluid collection, gallbladder wall thickening, and/or edema (double-wall sign) ^[73] HIDA scan : nonvisualization of the gallbladder	See the “Acute management checklist for acute cholecystitis.”
Acute cholangitis ^[64]^[65]^[74]^[75] ^[70]^[76]^[77]	Charcot triad: RUQ pain, fever, and jaundice Reynold pentad	Labs ↑ WBC and CRP ↑ ALP, ↑ AST, ↑ ALT, ↑ GGT ↑ Total bilirubin Positive blood cultures RUQ ultrasound: biliary dilation and/or evidence of obstruction (e.g., choledocholithiasis), thickening of bile duct walls MRCP/ERCP : findings similar to those on ultrasound	See the “Acute management checklist for acute cholangitis.”

Genitourinary causes

Genitourinary causes of acute abdominal pain
	Clinical features	Diagnostic findings	Acute management
Ruptured ectopic pregnancy ^[78]	Sudden severe lower abdominal pain Vaginal bleeding or amenorrhea Lower abdominal guarding and tenderness Cervical motion tenderness, closed cervix Enlarged uterus Tachycardia, hypotension	↑ β-hCG Transabdominal/transvaginal ultrasound Free fluid within Morison pouch and/or pouch of Douglas (See also “FAST scan” in “POCUS.”) Empty uterine cavity, thickened endometrial lining Adnexal mass Tubal ring sign For the ultrasound technique, see “POCUS for early pregnancy.”	See the “Acute management checklist for ectopic pregnancy.”
Ovarian torsion ^[79]^[80]	Sudden onset unilateral lower abdominal or pelvic pain Nausea, vomiting Unilateral iliac fossa tenderness	Pelvic (or transvaginal) ultrasound with Doppler velocimetry: enlarged, edematous ovaries with decreased blood flow Pelvic CT scan with IV contrast Unilateral thickened ovarian tube, enlarged ipsilateral ovary, and decreased enhancement of ipsilateral ovary Twisted vascular pedicle (whirlpool sign)	See the “Acute management checklist for ovarian torsion.”
Testicular torsion ^[81]	Severe lower quadrant and testicular pain Nausea and vomiting Abnormally elevated position of the testis within the scrotum	Clinical diagnosis Doppler ultrasound: twisting of the spermatic cord, reduced perfusion of the affected testicle	See the “Acute management checklist for testicular torsion.”
Acute pyelonephritis ^[12]^[82]^[83]^[84]^[85]	High fever, chills Flank pain with costovertebral angle tenderness (usually unilateral, may be bilateral) Dysuria, urinary frequency, urgency	Labs ↑ WBC, CRP, ESR Positive urinalysis Positive urine culture Renal ultrasound: edema and focal hypoechogenic areas CT pelvis with IV contrast: focal area(s) of hypoenhancement that extend to the cortical periphery	See the “Acute management checklist for acute pyelonephritis.”
Nephrolithiasis	Severe unilateral and colicky flank pain (renal colic) Hematuria Nausea, vomiting Dysuria, frequency, and urgency	Urine dipstick and urinalysis: gross or microscopic hematuria Urine microscopy: to detect crystals Abdominopelvic CT: Nonenhanced CT scan is the gold standard. Ultrasound: method of choice for patients in whom radiation exposure should be minimized (e.g., pregnant patients, children, recurrent stone formers)	See “Treatment”-section in “Nephrolithiasis.”
Pelvic inflammatory disease	Recent sexual activity Pelvic or lower abdominal pain Cervical motion tenderness Uterine tenderness Adnexal tenderness Mucopurulent cervical/vaginal discharge Fever	Clinical diagnosis (See “Diagnostic criteria for PID.”) Pregnancy test NAAT for gonorrhea and chlamydia Wet mount: for leukorrhea, trichomoniasis, bacterial vaginosis HIV testing and syphilis testing Additional evaluation for PID (e.g., with pelvic ultrasound) if tuboovarian abscess is suspected	See “Treatment of PID.”
Acute urinary retention ^[7]^[86]^[87]	Commonly seen in older men Painful inability to void Suprapubic pain Palpable distended bladder Restlessness and/or acute distress	Urinalysis and culture: to evaluate for UTI, hematuria, and glucosuria BMP: ↑ BUN and creatinine in cases of renal failure due to obstruction Ultrasound of urinary tract: bladder distention	Urgent bladder catheterization Urology referral for management of the underlying condition

POCUS (abdomen): free fluid in hepatorenal recess (Morison pouch)

Treatment

Definitive treatment of abdominal pain is cause-specific (e.g., see “Gastrointestinal causes of acute abdominal pain”). Consider the following general therapies on an individual basis:

Supportive care for acute abdominal pain

Parenteral analgesics
Empiric antibiotics for intraabdominal infections
Antiemetics
NG tube placement
Urinary catheter placement (e.g., Foley catheter)

Empiric antibiotics for intraabdominal infections

Determine if the infection is community-acquired or healthcare-associated and how severe it is.
Consider organisms commonly implicated in intraabdominal infection (e.g., E. coli).
Consider local resistance patterns.
See also “Empiric antibiotic therapy for acute biliary infection.”

Community-acquired infections ^[88]^[89]^[90]

Consider coverage of the following organisms:
- Enteric gram-positive streptococci
- Enteric gram-negative aerobic and facultative bacilli
- Fluoroquinolone-resistant E. coli
Enterococcal coverage is not usually necessary for mild to moderate community-acquired infection but is recommended for severe infection.
Fluoroquinolones are only recommended as a single-agent regimen if the hospital antibiogram indicates > 90% susceptibility of E. coli. ^[88]

Severity of infection	Suggested single-agent empiric regimen ^[88]	Suggested combination empiric regimen ^[88]
Mild or moderate infection	Cefoxitin Ertapenem Moxifloxacin Tigecycline Ticarcillin/clavulanate	Metronidazole PLUS one of the following Cefazolin Cefotaxime Ceftriaxone Cefuroxime Ciprofloxacin Levofloxacin
Severe infection and/or high-risk patient	Doripenem Imipenem Meropenem Piperacillin/tazobactam	Metronidazole PLUS one of the following Cefepime Ceftazidime Ciprofloxacin Levofloxacin

Metronidazole is contraindicated in the first trimester of pregnancy.

Healthcare-associated infections ^[70]^[88]^[89]^[90]

Healthcare-associated infections are more likely to be antibiotic-resistant. Consider institutional antibiograms when choosing an empiric regimen.

Consider coverage of the following organisms:
- Enteric gram-positive streptococci
- Enteric gram-negative aerobic and anaerobic bacilli (including Pseudomonas aeruginosa)
- Enterococci
- MRSA
Agents to avoid as empiric therapy
- Cephalosporins as a single-agent regimen
- Fluoroquinolones as a single-agent regimen
- Ampicillin-sulbactam

Patient and/or institutional risk factors	Suggested empiric regimens ^[88]
Low risk (< 20%) of infection with resistant organism	1) Single-agent regimen Carbapenems Doripenem Imipenem Meropenem OR piperacillin/tazobactam
Low risk (< 20%) of infection with resistant organism	2) Combination regimen Metronidazole PLUS one of the following: Ceftazidime Cefepime
High risk (> 20%) of infection with resistant organism	Single-agent or combination empiric regimen (see above) PLUS one of the following: Aminoglycoside Gentamicin Tobramycin Amikacin OR polymyxin ^[89] ^[91] OR a new combination beta-lactam Ceftolozane/tazobactam Ceftazidime/avibactam
High risk of MRSA	Combination empiric regimen (see above) PLUS vancomycin

Obtain cultures, if necessary, before the administration of empirical IV antibiotics.

For patients with a beta-lactam or carbapenem allergy, consider vancomycin with aztreonam and metronidazole.

Surgery

The definitive management of most causes of acute abdomen is surgical.
The choice of procedure and the urgency of surgery is determined by the underlying condition.
Patients with signs of diffuse peritonitis or sepsis require immediate surgical management, which should not be delayed by time-consuming diagnostic tests.
Examples of urgent consultations:
- General surgery for hemodynamically unstable patients with a rigid abdomen
- Vascular surgery for a ruptured or symptomatic AAA
- OB/GYN for a ruptured ectopic pregnancy

Differential diagnoses

Non-life-threatening causes of acute abdomen Differential diagnoses of acute abdomen by region

	Gastrointestinal etiologies ^[22]	Nongastrointestinal etiologies ^[22]
RUQ	Biliary colic Acute cholecystitis Acute cholangitis Emphysematous cholecystitis Acute hepatitis Pyogenic liver abscess Duodenal ulcer Portal vein thrombosis	Lower lobe pneumonia Lower lobe pulmonary infarction (pulmonary embolism) Empyema Ureteric colic Pyelonephritis
LUQ	Gastric ulcer Splenic abscess Splenic laceration Splenic infarction
RLQ	Acute appendicitis Colitis IBD Epiploic appendagitis Neutropenic enterocolitis	Ureteric colic (nephrolithiasis) Ectopic pregnancy Ovarian torsion Ruptured ovarian cyst PID Testicular torsion
LLQ	Diverticulitis Colitis IBD Epiploic appendagitis
Epigastrium	Acute esophagitis Acute gastritis Acute pancreatitis Acute mesenteric ischemia PUD GERD Functional dyspepsia Mallory Weiss syndrome	Myocardial infarction Pericarditis AAA Aortic dissection
Periumbilical	Acute appendicitis (early) Mesenteric ischemia	AAA Aortic dissection
Suprapubic	Diverticulitis	Ectopic pregnancy PID Cystitis (UTI) Prostatitis Endometriosis Acute urinary retention
Diffuse abdominal pain	Bowel obstruction Bowel perforation (peritonitis) Mesenteric ischemia (peritonitis) Irritable bowel syndrome Constipation Gastroenteritis Spontaneous bacterial peritonitis	Diabetic ketoacidosis Sickle cell crisis Porphyria Cocaine use Opioid withdrawal Cannabinoid hyperemesis syndrome Endometriosis Retroperitoneal hematoma Acute adrenal insufficiency Heavy metal poisoning

The differential diagnoses listed here are not exhaustive.

Special patient groups

Acute abdominal pain in adults ≥ 65 years

Overview ^[5]^[92]^[93]

Common etiologies of acute abdomen can manifest with atypical presentations.
Always consider the following etiologies in adults ≥ 65 years:
- Life-threatening vascular conditions (e.g., mesenteric ischemia, ruptured AAA)
- Malignancy
- Nonabdominal causes of abdominal pain, e.g.:
  - Acute MI ^[92]
  - Urinary retention
  - Herpes zoster
Older patients have an increased risk of morbidity and mortality, which can be related to:
- Higher incidence of serious causes of acute abdomen in this age group ^[92]^[93]
- Delayed presentation secondary to barriers to accessing healthcare ^[5]
- Increased risk of misdiagnosis and delayed diagnosis ^[5]
- Comorbidities

Clinical features of acute abdominal pain in older adults

Atypical clinical presentations are more common. ^[5]^[92]
Absence of expected findings, for example:
- Pain
- Fever
- Tachycardia ^[5]
- Localizing signs
- Rigidity or guarding on abdominal exam ^[5]
Presence of atypical findings, for example:
- Hypothermia
- Altered mental status or delirium ^[94]
- Other nonspecific symptoms, e.g., back pain

Examples of altered presentations of acute abdomen in adults ≥ 65 years ^[5]^[92]^[93]
Condition	Features
Acute cholecystitis ^[5]	Fever, nausea, and vomiting are frequently absent. ^[5]^[93] Higher risk of complications ^[5]^[93]
Appendicitis	Fever, nausea, and rebound tenderness may be absent. ^[93] RLQ pain is typically present. ^[93] Higher risk of complications (e.g., perforation) and mortality ^[93]
Diverticulitis	Fever may be absent. ^[93] Higher risk of complications ^[92]
Small bowel obstruction	Gallstone ileus and malignancy are potential etiologies. ^[92] Higher risk of mortality ^[93]
Large bowel obstruction	Vomiting and constipation may be absent. ^[92] Sigmoid volvulus is a potential etiology. ^[93]^[95]
Peptic ulcer disease	Abdominal pain, nausea, and vomiting may be absent. ^[5]^[93] Abdominal rigidity is frequently absent with perforation. ^[93] Up to half of patients present with complications (e.g, perforation). ^[93] Higher risk of mortality ^[93]
Pancreatitis	Abdominal pain and vomiting may be absent. ^[93] Higher risk of severe disease ^[93] Additional etiologies in this age group include drug-induced pancreatitis and ischemia. ^[93]

It is essential to maintain a broad differential diagnosis when evaluating older adults with acute abdominal pain.

Older adults with life-threatening conditions (e.g., mesenteric ischemia, appendicitis, ruptured abdominal aortic aneurysm) may present with a relatively unremarkable physical exam. ^[5]

Diagnostics ^[92]^[93]

Obtain an ECG in all older adults with epigastric pain or PUD. ^[92]^[93]
Interpret lab results with caution.
- Studies may be normal when pathology is present, e.g.:
  - Leukocytosis may be absent, even in acute cholecystitis, diverticulitis, and appendicitis. ^[92]^[93]
  - Liver chemistries may be normal in cholecystitis. ^[92]
- Abnormal studies may not be clinically significant, e.g.:
  - Asymptomatic bacteriuria is common.
  - CBC, renal function tests, and liver chemistries may be abnormal at baseline. ^[96]^[97]^[98]
Maintain a low threshold for imaging studies; CT abdomen and pelvis with IV contrast is preferred. ^[99]
See also “Diagnostics for acute abdominal pain.”

Leukocytosis may be absent in older adults with acute cholecystitis, appendicitis, and diverticulitis. ^[92]^[93]

Asymptomatic bacteriuria is often found in older adults, but should not be considered a cause of acute abdominal pain. ^[92]

Treatment ^[92]^[93]

Maintain a lower threshold for advanced management, including: ^[93]
- Early surgical consultation
- Admission
Consider age and comorbidities when prescribing.
- Age affects the selection of empiric antibiotics for intraabdominal infections. ^[88]^[100]
- Dosages of medication (antibiotics, analgesia) may need adjusting; see “Prescribing for older adults.”
- Use less aggressive fluid resuscitation rates in conditions such as pancreatitis. ^[93]
Discuss advance care planning with patients and next of kin.
See also “Treatment of acute abdomen.”

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