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A 61-year-old man with a history of hypertension, diabetes, peripheral vascular disease, and congestive heart failure presents to the Emergency Department with left lower-extremity pain at rest and with a nonhealing ulcer of the left foot. The patient is admitted to the hospital for treatment of the ulcer and for a workup of his peripheral vascular disease.

Plain radiographs of the patientís left foot and left lower leg show evidence of osteomyelitis of the distal first phalanx and distal tibia. After general and vascular surgeons evaluate him, they decide to proceed with a below-the-knee amputation on the left side. On postoperative day 2, the patient reports having severe midepigastric abdominal pain, as well as nausea, vomiting, and diarrhea, with no hematemesis or hematochezia.

On physical examination, the patient is afebrile but hypotensive, with a blood pressure of 88/54 mm Hg. He has slight tachycardia at a rate of 120 bpm. His oxygen saturation while breathing room air is 90%. His abdomen is distended, with diffuse rebound tenderness. Hypoactive bowel sounds are auscultated. The rest of his physical findings, including the condition of his postoperative wounds, are unremarkable. Laboratory results, including CBC and electrolyte levels, are within normal limits.

Plain radiographs of the abdomen are obtained (see Image 1), followed by contrast-enhanced CT scans of the abdomen and pelvis (see Images 2-3).

What is the diagnosis?

 


Answer

Portal venous air with pneumatosis intestinalis: The plain radiograph of the abdomen shows mildly dilated loops of small bowel and a bubbly appearance on the left side, which suggests air in the bowel wall, also known as pneumatosis (see Image 1, arrowheads). Contrast material in the urinary tract is from a recent angiographic study that was performed to evaluate the patient for peripheral vascular disease. The right upper quadrant contains several branching and linear lucent areas overlying or in the liver; these likely represent biliary or portal venous air (arrows). Subsequent CT scans confirm these findings, showing air in the superior mesenteric vein and intrahepatic ramifications of the portal vein (see Images 2-3). Circumferential pneumatosis is seen in the proximal aspect of the small bowel.

Differentiating biliary air from portal venous air is critical because biliary air is usually benign but portal venous air is commonly a harbinger of a grave outcome. Because bile flows centrally to the common bile duct, biliary air lies centrally in the liver. Biliary air is characteristically found more than 2 cm from the hepatic capsule. By comparison, because portal blood flows peripherally, portal venous air should at least partially lie within 2 cm of the hepatic capsule. The pattern of distribution is often equivocal, and further imaging with CT is necessary to differentiate the 2 conditions. In the optimal case, the air can be traced back and localized to the biliary tree or portal venous system on CT scans.

Portal venous air is not a disease in itself but, rather, is a result of various causes, some harmless and others not. The most worrisome and most common underlying cause is bowel ischemia (with or without infarction). Bowel ischemia and infarction likely cause the mucosal barrier to break down, allowing air and toxins to leak into the portal venous system. Portal venous air is sometimes seen after a barium enema study or colonoscopy and in association with bowel obstruction, necrotizing enterocolitis in children, diverticulitis, intra-abdominal abscesses, or toxic megacolon.

Pneumatosis intestinalis is characterized by the presence of extraluminal gas in the submucosal and/or subserosal layers of the bowel wall. It is considered an ominous finding in patients with ischemia, particularly if it is associated with portomesenteric gas. Pneumatosis intestinalis is also seen in other conditions or situations, such as chronic obstructive pulmonary disease, connective tissue disorders, infectious enteritis, celiac disease, leukemia, organ transplantation, amyloidosis, steroid treatment, chemotherapy, and AIDS.

Pneumatosis intestinalis occurs in 2 forms: primary and secondary. Primary pneumatosis intestinalis, which occurs in 15% of patients, is a benign idiopathic condition in which several thin-walled cysts form in the submucosa or subserosa of the intestinal wall. This type is usually not associated with symptoms, and it may be found incidentally during radiography or endoscopy. This primary form is often called pneumatosis cystoides intestinalis. The secondary form, which occurs in 85% of patients, is associated with obstructive pulmonary disease, as well as obstructive and necrotic GI diseases.


For more information, see the eMedicine articles Mesenteric Ischemia and Pneumatosis Intestinalis.

References

  • Alobaidi M,, Jafri SZ: Mesenteric Ischemia. eMedicine Journal [serial online]. 2003. Available at: www.emedicine.com/radio/topic446.htm Accessed: September 19, 2006.
  • Goyal SK,, Weltman DI: Pneumatosis Intestinalis. eMedicine Journal [serial online]. 2005. Available at: www.emedicine.com/radio/topic560.htm. Accessed September 19, 2006.
  • Kernagis LY, Levine MS, Jacobs JE: Pneumatosis intestinalis in patients with ischemia: correlation of CT findings with viability of the bowel. AJR Am J Roentgenol 2003; 180: 733-6. [MEDLINE 12591685]
  • Sebastia C, Quiroga S, Espin E, et al: Portomesenteric vein gas: pathological mechanisms, CT findings, and prognosis. Radiographics 2000; 20: 1213-24. [MEDLINE 10992012]
  • Wiesner W, Mortele KJ, Glickman JN, et al: Pneumatosis intestinalis and portomesenteric venous gas in intestinal ischemia: Correlation of CT findings with severity of ischemia and clinical outcome. AJR Am J Roentgenol 2001;177: 1319-23. [MEDLINE 11717075]

Authors:
Charlie Clarke, MD
Radiology Resident
UT Southwestern Medical Center,
Dallas, TX

Pramod Gupta, MD
Staff Radiologist
Dallas VA Medical Center,
Clinical Assistant Professor
University of Texas Southwestern,
Dallas, TX

eMedicine Editors:
Erik D. Schraga, MD,
Department of Emergency Medicine,
Kaiser Permanente,
Santa Clara Medical Center, Calif

Rick G. Kulkarni, MD
Assistant Professor,
Yale School of Medicine,
Section of Emergency Medicine,
Department of Surgery,
Attending Physician,
Medical Director,
Department of Emergency Services,
Yale-New Haven Hospital, Conn

 

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