Differentials
Acute viral syndromes
SIGNS / SYMPTOMS
Very difficult to differentiate; lack of exposure to specific foods or absence of specific behaviors may help in differentiating.
INVESTIGATIONS
Occasionally, acute viral serology, in particular IgM, (presence or rise from baseline) may help diagnose specific viruses.
Crohn disease
SIGNS / SYMPTOMS
May present with fatigue, diarrhea, abdominal pain, weight loss, fever, and rectal bleeding. Other signs may include presence of oral ulcers, perianal skin tags, fistulae, abscesses, and sinus tracts; abdominal exam may reveal a palpable mass in the ileocecal area; no mass present on digital rectal exam.
INVESTIGATIONS
Stool culture, microscopy, and antigen testing: negative.
Upper gastrointestinal and small bowel series: edema and ulceration of the mucosa with luminal narrowing and strictures. CT/MRI abdomen: skip lesions, bowel wall thickening, surrounding inflammation, abscess, fistulae.
Colonoscopy: aphthous ulcers, hyperemia, edema, cobblestoning, skip lesions.
Ulcerative colitis
SIGNS / SYMPTOMS
May present with bloody diarrhea, history of lower abdominal pain, fecal urgency, presence of extraintestinal manifestations (e.g., erythema nodosum, acute arthropathy), history of primary sclerosing cholangitis. No mass present on digital rectal exam.
INVESTIGATIONS
Stool culture, microscopy, and antigen testing: negative.
Histology: continuous distal disease, mucin depletion, basal plasmacytosis, diffuse mucosal atrophy, absence of granulomata, and anal sparing.
Colonoscopy: rectal involvement, continuous uniform involvement, loss of vascular marking, diffuse erythema, mucosal granularity, normal terminal ileum (or mild "backwash" ileitis in pancolitis).
Food allergies/intolerance
SIGNS / SYMPTOMS
History of exposure to certain foods known to cause intolerance or allergies (milk, lactose, gluten) and relapsing symptoms with challenge.
INVESTIGATIONS
Celiac markers are positive in most patients with gluten intolerance.
Hydrogen breath test helps in diagnosing lactose intolerance.
Colonoscopy and biopsies help in diagnosing milk allergies.
Irritable bowel syndrome
SIGNS / SYMPTOMS
Total duration of symptoms should be more than 6 months with specific criteria of combination of abdominal bloating or pain relieved by defecation and association with change in stool frequency and/or consistency without evidence of alarm signs or symptoms.
Physical exam reveals a healthy nontoxic appearance without evidence of dehydration.
INVESTIGATIONS
All imaging and laboratory tests are usually within normal range.
Microscopic colitis
SIGNS / SYMPTOMS
Typically present in older persons, long duration symptoms, and lack of hematochezia.
INVESTIGATIONS
Colonoscopy revealing normal appearing mucosa and biopsies showing lymphocytic infiltrates and/or thickened collagenous layer are diagnostic.
Acute appendicitis
SIGNS / SYMPTOMS
Localized right lower quadrant pain and peritoneal irritation are classic (guarding).
INVESTIGATIONS
CT scan of the abdomen is diagnostic.
Elevated serum and urine WBCs.
Acute cholecystitis
SIGNS / SYMPTOMS
Localized pain in the right upper quadrant and a positive Murphy sign are classic symptoms.
INVESTIGATIONS
Ultrasound showing gallbladder wall thickening; elevated alkaline phosphatase, bilirubin, alanine aminotransferase, and aspartate aminotransferase when biliary obstruction is present (choledocholithiasis).
Acute pancreatitis
SIGNS / SYMPTOMS
Epigastric pain radiating to the back, history of excessive alcohol consumption in alcohol induced pancreatitis may help.
Acute hepatitis
SIGNS / SYMPTOMS
Jaundice is usually present.
Risk factors for acute hepatitis B and C include unprotected sex and intravenous drug use.
History of excessive alcohol consumption in alcoholic hepatitis.
History of hepatotoxic medication use or overdose in drug induced hepatitis.
Neurologic signs and Kayser-Fleischer ring in Wilson disease.
INVESTIGATIONS
Serology for acute hepatitis (acute hepatitis panel), serologic markers of autoimmune hepatitis, serum ceruloplasmin, drug levels (in particular, acetaminophen) can help.
When leukopenia and thrombocytopenia present, tick-borne/rickettsial infections (Rocky Mountain spotted fever and Ehrlichia) are considered.
Malabsorption syndromes
SIGNS / SYMPTOMS
Chronic symptoms and significant malnourishment, history of intestinal surgery and extraintestinal manifestations of malnourishment, and malabsorption are usually present.
INVESTIGATIONS
Stool alpha antitrypsin, low serum prealbumin, albumin and total protein, multiple vitamins, and elements deficiency.
Large bowel obstruction
SIGNS / SYMPTOMS
Distention is the more common presenting symptom, with vomiting, including vomiting of fecal matter, occurring later in the course of the illness.
INVESTIGATIONS
Plain abdominal x-ray: gaseous distension of large bowel; kidney-bean shape seen in volvulus.
Small bowel obstruction (SBO)
SIGNS / SYMPTOMS
Presents with abdominal distension and vomiting earlier on in course of the illness; may be history of abdominal surgery.
INVESTIGATIONS
Plain abdominal x-ray: air-fluid levels, dilated intestinal loops, absence of gas in the rectum (in complete SBO), pneumoperitoneum. However, food poisoning may be associated with ileus and functional obstruction and same imaging findings.
Radiation enteritis
SIGNS / SYMPTOMS
Patients have a history of receiving radiation therapy.
INVESTIGATIONS
Endoscopy and biopsy; histologic findings support this diagnosis.
Mesenteric ischemia
SIGNS / SYMPTOMS
Sudden onset of diffuse abdominal pain suggests acute mesenteric ischemia or non-occlusive mesenteric ischemia. However, chronic symptoms of vague, diffuse abdominal pain may be indicative of chronic mesenteric ischemia. In contrast, ischemic colitis may cause focal or diffuse abdominal pain and often has a more insidious onset, over several hours or days.
INVESTIGATIONS
CT scan/endoscopy. Typical finding is thickening of the bowel wall in a segmental pattern.
Endoscopic findings include pale mucosa with petechial bleeding. Bluish hemorrhagic nodules may be seen representing submucosal bleeding; these correspond to thumbprints seen on radiographic studies.
Medication and drugs side-effects/toxicity
SIGNS / SYMPTOMS
History of drug ingestion/use.
INVESTIGATIONS
Urine and serum screen, blood drug level.
Diverticulitis
SIGNS / SYMPTOMS
Leukocytosis and fever in an older patient.
INVESTIGATIONS
CT scan/WBC.
Systemic vasculitis
SIGNS / SYMPTOMS
Multisystem involvement (skin, joints, blood) and chronic presentation.
INVESTIGATIONS
Biopsy shows vasculitis pattern (leukocytoclastic, necrotizing).
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