Right upper quadrant (RUQ) abdominal pain presents a significant diagnostic challenge due to the array of potential underlying conditions. While common causes often dominate the differential diagnosis, it is crucial for clinicians to consider rarer, yet serious, conditions to ensure timely and effective patient management. Polyarteritis nodosa (PAN), a systemic necrotizing vasculitis of medium-sized arteries, is an infrequent cause of abdominal pain that should be considered, particularly in cases of unexplained or intractable RUQ pain. This discussion highlights an atypical presentation of PAN in a middle-aged man, primarily manifested as severe RUQ pain without typical systemic features, emphasizing the importance of including PAN in the Ruq Pain Differential Diagnosis.
Our patient presented with significant RUQ abdominal pain, prompting an extensive investigation to determine the etiology. Interestingly, typical systemic manifestations often associated with PAN, such as fever, weight loss, neuropathy, renal involvement, or skin lesions, were notably absent in this case. Further complicating the diagnostic process was the presence of various autoantibodies, including p-ANCA, ANA, and anti-Ro antibodies. The detection of these autoantibodies initially suggested alternative diagnoses, such as ANCA-associated vasculitides (granulomatosis with polyangiitis, microscopic polyangiitis, eosinophilic granulomatosis with polyangiitis) or vasculitis secondary to autoimmune connective tissue diseases (systemic lupus erythematosus, Sjögren’s syndrome, mixed connective tissue disease). However, it’s important to recognize that, while not typical, the presence of these autoantibodies has been documented in cases of PAN. Furthermore, the patient lacked clinical features characteristic of these alternative vasculitic syndromes, such as asthma, sinusitis, airway involvement, glomerulonephritis, arthritis, cutaneous lesions, or sicca symptoms. Moreover, serological tests for autoimmune connective tissue diseases, including serum complements, rheumatoid factor, anti-dsDNA, anti-Smith, anti-RNP, anti-La, and antiphospholipid antibodies, were all negative, further reducing the likelihood of these conditions.
Angiographic findings played a crucial role in narrowing the differential diagnosis and pointing towards PAN. Consistent with typical PAN involvement, angiography revealed abnormalities in the medium and small vessels of the superior mesenteric and hepatic arterial territories. These findings included arterial calibre changes, characteristic “corkscrew” vessels, and distal microaneurysms. Notably, in PAN, the superior mesenteric artery is more frequently affected than the inferior mesenteric artery, with the jejunal arteries being the most commonly involved, followed by the ileal arteries. Hepatic vasculature involvement is also significant in PAN, occurring in up to 53% of patients. This hepatic involvement can affect arteries supplying the bile ducts, gallbladder, and liver, potentially leading to acalculous cholecystitis, gallbladder infarcts, aneurysms, intrahepatic hematomas, and infarcts, all of which can manifest as RUQ pain.
Abdominal pain is a common presenting symptom of PAN, and a significant proportion of patients, if left untreated, can progress to acute abdomen. Studies have highlighted the severity of gastrointestinal involvement in PAN. For instance, research indicates that over half of PAN patients with gastrointestinal involvement may develop acute abdomen, which carries a substantial mortality risk. Specifically concerning RUQ pain, numerous reports have documented it as the initial presentation of PAN. In some instances, the diagnosis of PAN is unexpectedly made during or after cholecystectomy performed for presumed acalculous cholecystitis. This underscores the potential for gallbladder involvement and hepatic aneurysm rupture as causes of RUQ pain in PAN.
Prompt diagnosis and initiation of immunosuppressive treatment are critical in managing PAN and improving patient outcomes. Historically, mortality within the first year of PAN diagnosis is often linked to vasculitic complications, particularly those involving the gastrointestinal system, rather than complications from immunosuppression itself. In this particular case, immunosuppressive treatment with corticosteroids and cyclophosphamide, initiated after a delay of two months from symptom onset, proved remarkably effective. Fortunately, the patient did not develop life-threatening complications such as ruptured hepatic aneurysm or bowel infarction or rupture. Research consistently demonstrates that early treatment with immunosuppressive agents significantly reduces the risk of aneurysm formation, lessens associated comorbidities, and improves survival rates compared to delayed treatment.
In conclusion, while the differential diagnosis of RUQ abdominal pain is broad, Polyarteritis Nodosa, although rare, should be a considered, especially in patients presenting with persistent and unexplained RUQ pain that does not respond to typical treatments like antibiotics and analgesics. This case, along with existing literature, reinforces the importance of considering PAN in the differential diagnosis of RUQ pain. Early recognition and prompt initiation of appropriate immunosuppressive therapy are crucial to halt the progression of inflammatory vasculopathy, thereby minimizing the risks of aneurysm formation and rupture, and ultimately reducing morbidity and mortality associated with PAN.
Learning Points
- Polyarteritis nodosa (PAN) is a serious systemic vasculitis affecting medium and small-sized vessels and can involve multiple organ systems.
- In rare instances, PAN may present primarily or initially in a single organ system, including the gastrointestinal tract, making diagnosis challenging.
- In patients presenting with right upper quadrant abdominal pain, especially when intractable or unexplained, clinicians should consider PAN in the differential diagnosis.
- Timely diagnosis and treatment of PAN, particularly in cases with gastrointestinal involvement, are crucial for reducing morbidity and mortality.
