MEDizzy - A 54-year-old man is admitted for persistent lower abdominal

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A 54-year-old man is admitted for persistent lower abdominal and groin pain that began 7 months previously. Two months before his present admission, he required exploratory laparoscopy for acute abdominal pain and presumed cholecystitis. This revealed necrotic omental tissue and pericholecystitis necessitating omentectomy and cholecystectomy. However, the pain continued unchanged. He currently describes it as periumbilical and radiating into his groin and legs. It becomes worse with eating. The patient has also had episodic severe testicular pain, bowel urgency, nausea, vomiting, and diuresis. He has lost approximately 22.7 kg over the preceding 6 months. His past medical history is significant for hypertension that has recently become difficult to control. Medications on admission include aspirin, hydrochlorothiazide, hydromorphone, lansoprazole, metoprolol, and quinapril. On physical examination, the patient appears comfortable. His blood pressure is 170/100 mmHg, his heart rate is 88 beats/min, and he is afebrile. He has normal first and second heart sounds without murmurs, and an S4 is present. There are no carotid, renal, abdominal, or femoral bruits. His lungs are clear to auscultation. Bowel sounds are normal. Abdominal palpation demonstrates minimal diffuse tenderness without rebound or guarding. No masses are present, and the stool is negative for occult blood. During the examination, the patient develops Raynaud’s phenomenon in his right hand that persists for several minutes. His neurologic examination is intact. Admission laboratory studies reveal an erythrocyte sedimentation rate of 72 mm/h, a BUN of 17 mg/dL, and a creatinine of 0.8 mg/dL. The patient has no proteinuria or hematuria. Tests for antinuclear antibodies, anti–double-strandedDNA antibodies, and antineutrophil cytoplasmic antibodies are negative. Liver function tests are abnormal with an AST of 89 IU/L and an ALT of 112 IU/L. Hepatitis B surface antigen and e antigen are positive. Mesenteric angiography demonstrates small, beaded aneurysms of the superior and inferior mesenteric veins. What is the most likely diagnosis?

ExplanationThis patient has polyarteritis nodosa associated with hepatitis B infection. Polyarteritis nodosa (PAN) is a small- and medium-vessel vasculitis that classically involves the muscular mesenteric and renal arteries. Pulmonary arteries are spared. Classic PAN is a rare disease, but its exact prevalence is unknown because reported cases frequently also include other vasculitides such as microscopic polyangiitis. Prior to the Chapel Hill Consensus Conference of 1992, microscopic polyangiitis and PAN were considered as the same disease, but it has been recognized that these are two separate diseases with different serologic markers and vascular predilection. Clinical manifestations of PAN are commonly vague, and often patients have been ill for several months prior to diagnosis. Symptoms include fatigue, weight loss, abdominal pain, headache, and hypertension. The pathologic lesion of PAN is necrotizing inflammation of the small- and medium-sized muscular arteries, and diagnosis relies on demonstration of this lesion on biopsy. However, in the absence of easily obtainable tissue, the presence of multiple aneurysmal dilatations on mesenteric angiogram is highly suggestive of PAN in the appropriate clinical setting. There are no serologic tests that are diagnostic of PAN. It is rare to have positive antibodies to pANCA or cANCA in PAN. Interestingly, 30% of cases of PAN are associated with active hepatitis B infection, as in this patient, and it is thought that circulating immune complexes may play a role in the pathogenesis of this disease. Unlike PAN, microscopic polyangiitis (MPA) involves venules and capillaries in addition to small arteries. The histopathologic lesion of MPA is a necrotizing vasculitis that is pauci immune with minimal deposition of immune complexes. Typical presenting features are rapidly progressive glomerulonephritis and pulmonary hemorrhage, which are distinctly uncommon features of PAN. Antimyeloperoxidase antibodies (pANCA) are frequently present. Mixed cryoglobulinemia is a small-vessel vasculitis most often associated with hepatitis C infection. Skin involvement with leukocytoclastic vasculitis and palpable purpura are the most common presenting features. Proliferative glomerulonephritis is present in 20–60% of individuals and is the most common cause of morbidity. Ischemic colitis typically presents with abdominal pain out of proportion to the examination as in this case, but the mesenteric angiogram would show atherosclerotic narrowing rather than aneurysmal dilatation. Hepatocellular carcinoma is not associated with vasculitis and typically presents with vague abdominal pain and obstructive jaundice.