General Comments

Clinical signs vary greatly depending on the type and severity of the disease leading to an acute abdomen.

Historical Findings

• Trembling, reluctance to move, inappetence, vomiting, diarrhea, vocalizing, and abnormal postures (tucked up or praying position)-signs that the owner may notice.
• Question owner carefully to ascertain what system is affected; for example, melena with a history of NSAID treatment may suggest GI mucosal disruption (ulceration).

Physical Examination Findings

• Abnormalities include abdominal pain, splinting of the abdominal musculature, gas- or fluid-filled abdominal organs, abdominal mass, ascites, pyrexia or hypothermia, tachycardia, and tachypnea.
• Once abdominal pain is confirmed, attempt to localize the pain to cranial, middle, or caudal abdomen.
• Perform a rectal examination to evaluate the colon, pelvic bones, urethra, and prostate, as well as for the presence of melena.
• Rule out extra-abdominal causes of pain by careful palpation of the kidneys and thoracolumbar vertebrae.
• Pain associated with intervertebral disc disease often causes referred abdominal guarding and is often mistaken for true abdominal pain. Renal pain can be associated with pyelonephritis.

Gastrointestinal

• Stomach-gastritis, ulcers, perforation, foreign bodies, gastric dilatation-volvulus.
• Intestine-obstruction (foreign bodies, intussusception, hernias), enteritis, ulcers, perforations.
• Rupture after obstruction, ulceration, or blunt or penetrating trauma, or due to tumor growth.
• Vascular compromise from infarction, mesenteric volvulus, or torsion.

Pancreas

• Pain associated with inflammation, abscess, ischemia.
• Pancreatic masses or inflammation obstructing the biliary duct/papilla may cause jaundice.

Hepatic and Biliary System

• Rapid distention of the liver and its capsule can cause pain.
• Biliary obstruction, rupture, or necrosis may lead to bile leakage and peritonitis. Gallbladder mucocele may be identified on ultrasound examination.
• Hepatic abscess.

Spleen

• Splenic torsion, splenic masses, splenic thrombus, splenic abscess.

Urinary Tract

• Distention is the main cause of pain in the urinary tract.
• Lower urinary tract obstruction can be due to tumors of the trigone area of the bladder or urethra, urinary calculi, or granulomatous urethritis.
• Traumatic rupture of the ureters or bladder are associated with blunt trauma and increased intra-abdominal pressure.
• Urethral tears can be associated with pelvic fractures from acute trauma.
• Free urine in the peritoneal cavity leads to a chemical peritonitis.
• Acute pyelonephritis, acute renal failure, nephroliths, and ureteroliths are uncommon causes of acute abdomen.

Genital Tract

• Prostatitis and prostatic abscess, pyometra; a ruptured pyometra or prostatic abscess can cause endotoxemia, sepsis, and cardiovascular collapse.
• Infrequent causes include ruptures of the gravid uterus after blunt abdominal trauma, uterine torsion, ovarian tumor or torsion, and intra-abdominal testicular torsion (cryptorchid).

Abdominal Wall/Diaphragm

• Umbilical, inguinal, scrotal, abdominal, or peritoneal hernias with strangulated viscera.
• Trauma or congenital defects leading to organ displacement or entrapment in the hernia will lead to abdominal pain if the vascular supply of the organs involved becomes impaired or ischemic.

Abdominal Radiography

• May see abdominal masses or changes in shape or shifting of abdominal organs.
• Loss of abdominal detail with abdominal fluid accumulation is an indication for abdominocentesis.
• Free abdominal gas is consistent with a ruptured GI viscus or infection with gas-producing bacteria and is an indication for emergency surgery.
• Use caution when interpreting radiographs following abdominocentesis with an open needle. Free gas may be introduced with this technique.
• Use caution when evaluating postoperative radiographs; free gas is a normal postoperative finding.
• Ileus is a consistent finding with peritonitis.
• Characterize ileus as functional (due to metabolic or inflammatory causes) or mechanical (due to obstruction).
• Foreign bodies may be radiopaque.
• Upper GI barium contrast radiographs are useful in evaluating the GI tract, particularly for determination of GI obstruction.
• Loss of contrast or radiographic detail in the area of the pancreas can be observed with pancreatic inflammation.

Abdominal Ultrasound

• A sensitive diagnostic tool for the detection of abdominal masses, abdominal fluid, abscesses, cysts, lymphadenopathy, and biliary or urinary calculi.
• FAST ultrasound is a published technique meaning Focused Assessment with Sonography in Trauma.

Abdominal CT

• Very sensitive diagnostic tool that may be used especially when surgeon requires additional information.

Abdominocentesis/Abdominal Fluid Analysis

• Perform abdominocentesis on all patients presenting with acute abdomen. Four-quadrant approach may improve yield. Fluid can often be obtained for diagnostic evaluation even when only a small amount of free abdominal fluid exists, well before detectable radiographic sensitivity. Ultrasound is much more sensitive than radiography for the detection of fluid and can be used to direct abdominocentesis. Blind abdominocentesis can be performed safely without ultrasound guidance. Abdominal fluid analysis with elevated WBC count, degenerate neutrophils, and intracellular bacteria is consistent with septic peritonitis and is an indication for immediate surgery.
• Diagnostic peritoneal lavage can be performed by introducing sterile saline (10–20 ml/kg) and performing abdominocentesis with or without ultrasound guidance.
• Measurement of glucose concentration in abdominal effusion in comparison with peripheral blood may aid in the diagnosis of septic abdomen. A blood-to-abdominal fluid glucose difference of >20 mg/dL is consistent with septic effusion.
• Pancreatitis patients may have an abdominal effusion characterized as a non-septic (sterile) peritonitis.
• Creatinine concentration higher in abdominal fluid than in serum indicates urinary tract leakage.
• Similarly, higher bilirubin concentration in abdominal fluid than in serum indicates bile peritonitis.

Sedation and Abdominal Palpation

• Because of abdominal splinting associated with pain, thorough abdominal palpation is often not possible without sedation; this is particularly useful for detecting intestinal foreign bodies that do not appear on survey radiographs.

Exploratory Laparotomy

• Surgery may be useful diagnostically (as well as therapeutically) when ultrasonography (or other advanced imaging) is not available or when no definitive cause of the acute abdomen has been established with appropriate diagnostics.

Analgesics

• Pain medication may be indicated for control of abdominal discomfort.
• Opioids, such as hydromorphone or fentanyl, are often good choices.

Histamine H₂ Antagonists

• Reduce gastric acid production.
• Famotidine 0.5–1.0 mg/kg IV, SC or IM q12h.
• Ranitidine 2 mg/kg IV q12h

Proton Pump Inhibitor

Pantoprazole 1–1.5 mg/kg IV as a CRI over 24 hours.

Protectants

Sucralfate 0.25–1 g PO q8h.

Antiemetics

• Metoclopramide 0.2–0.4 mg/kg IV q6–8h (or 24-hour continuous rate infusion (1–2 mg/kg/24h).
• Maropitant: dogs, 1–2 mg/kg SC; cats, 1 mg/kg SC
• Ondansetron 0.5–1 mg/kg IV slowly q6–12h.
• Dolasetron 1 mg/kg IV q24h.

Antibiotics

• Antibiotics may be indicated if signs of infection (fever, elevated white blood cell count, positive culture) are seen or hemorrhagic diarrhea is present.
• Broad spectrum for Gram-positive, Gram-negative, and anaerobic bacteria.
• Gram stain and cultures prior to treatment if possible, but do not delay intervention pending results.