Fecal occult blood raises concern for malignancy, ischemia, ulcer disease, or inflammatory conditions, whereas perianal fistulae, abscess, or inflammation suggests possible Crohn’s disease. Rectal examination also may detect an intra-abdominal inflammatory process such as an appendiceal abscess that is not palpable over the anterior abdominal wall. Inguinal hernias as a cause of intestinal obstruction may be detected on genital examination, whereas pelvic examination of women is essential for diagnosing adnexal masses and pelvic inflammatory disease.

Additional testing

Determining the cause of abdominal pain commonly requires laboratory testing (Figure 6.1). However, diagnostic testing in the patient with chronic functional pain should be directed by alarm findings on exam and screening blood tests to avoid reinforcing the patient’s conviction that there is something organically wrong. A complete blood count may show leukocytosis, indicating an inflammatory condition, or leukopenia, suggesting a viral syndrome. Microcytic anemia raises the possibility of gut blood loss. The sedimentation rate may be elevated in inflammatory conditions.

Electrolytes, blood urea nitrogen, and creatinine are measured to assess fluid status and renal function. Elevated serum amylase or lipase or both usually are observed early in acute pancreatitis. Perforated ulcers, diabetic ketoacidosis, or mesenteric infarction also may cause hyperamylasemia. Elevated levels of bilirubin or alkaline phosphatase suggest disease of the pancreas or biliary tract, whereas aminotransferase elevations indicate hepatocellular disease. Serum pregnancy testing is performed in women of reproductive potential who present with unexplained abdominal pain. Specific laboratory tests can assist in diagnosing acute porphyria or heavy metal intoxication. Tryptase levels are elevated in mast cell activation syndrome. Urinalysis may show erythrocytes or crystals, suggesting calculi; leukocytes or bacteria, suggesting infection; or bilirubin, suggesting pancreaticobiliary disease. Patients with ascites and abdominal pain should undergo paracentesis to exclude spontaneous bacterial peritonitis. Culdocentesis can aid in assessing intra-abdominal hemorrhage.

Supine and upright (or decubitus) abdominal plain radiography is essential in all patients with acute abdominal pain and can detect pneumoperitoneum from lumenal perforation, calcified gallstones or renal stones, air–fluid levels with intestinal obstruction, generalized or localized distension with ileus, pneumobilia with biliary disease, and a ground-glass appearance with ascites. Barium radiographs may complement the findings of plain films when mechanical obstruction is suspected. Chest radiographs can eliminate pulmonary sources of acute abdominal pain.

Other imaging studies complement findings of the examination, laboratory testing, and plain films. Ultrasound is useful for suspected cholelithiasis, biliary dilation, ovarian cysts, abscess formation, and ectopic pregnancy, whereas computed tomography (CT) is more sensitive for pancreatic disease, retroperitoneal collections, intra-abdominal abscess, some vascular processes, trauma-induced hematomas, and changes in the mesentery or intestinal wall resulting from ischemia or inflammation (as with diverticulitis). Scintigraphy with ^99mTc-iminodiacetic acid derivatives detects cystic duct obstruction from cholecystitis. Angiography or mesenteric resonance angiography may be indicated for suspected vascular occlusion. Ultrasound is sensitive for diagnosing the impending rupture of an abdominal aortic aneurysm, but further study with aortography may delay definitive therapy and should be performed in the operating room, if indicated, because of the risk of exsanguination. Upper endoscopy is performed for chronic epigastric pain that suggests uncomplicated peptic ulcer, but is contraindicated with suspected perforation.

Sigmoidoscopy or colonoscopy is helpful with lower abdominal pain secondary to suspected ischemia, infection, volvulus, drug-induced colitis, or inflammatory bowel disease. Endoscopic retrograde cholangiopancreatography (ERCP) may be required for suspected cholangitis, whereas ERCP and endoscopic ultrasound (EUS) are sensitive for detecting choledocholithiasis. ERCP, EUS, and magnetic resonance cholangiopancreatography may provide complementary information in diagnosing chronic pancreatitis. Laparoscopy may be performed on an emergency basis in extremely ill patients or electively for chronic abdominal pain where the diagnosis is elusive after extensive diagnostic testing.

Differential diagnosis

The differential diagnosis of abdominal pain includes pathological processes within and outside the abdomen (Table 6.1). Generally, pain from diseases of the hollow organs (e.g. gut, urinary tract, pancreaticobiliary tree) results from obstruction, ulceration, inflammation, perforation, or ischemia. Pain from disorders of solid organs (e.g. liver, kidneys, spleen) is caused by distension from infection, obstruction to drainage, or vascular congestion. In women, the adnexa and uterus are potential sources of pain. Lung or cardiac abnormalities may secondarily cause referred pain in the upper abdomen. Metabolic conditions (e.g. lead poisoning, diabetic ketoacidosis) cause diffuse or localized abdominal pain. Acute intermittent porphyria, a disorder of heme biosynthesis that results in accumulation of toxic intermediates, causes colicky abdominal pain, ileus, and psychiatric disturbances. Familial Mediterranean fever produces painful inflammation of joints, skin, and serosal surfaces in the abdomen and the chest. Mast cell activation syndrome represents an emerging process of immune dysfunction whereby degranulation of mast cells results in inflammation that causes abdominal pain, dermatographia, and other systemic symptoms. Degenerative disk disease, tabes dorsalis, and varicella zoster virus reactivation elicit superficial abdominal wall pain.

Only gold members can continue reading. Log In or Register to continue