Right upper quadrant (RUQ) abdominal pain presents a common diagnostic challenge in clinical practice due to the diverse range of potential underlying conditions. While the differential diagnosis typically includes common pathologies such as gallbladder disease, liver conditions, and peptic ulcer disease, rarer entities can also manifest with RUQ pain, requiring a broader diagnostic approach. This article aims to highlight Polyarteritis Nodosa (PAN), a systemic necrotizing vasculitis, as an important, albeit less frequent, consideration in the Differential Diagnosis Of Right Upper Quadrant Pain, particularly in cases where typical etiologies are excluded or when pain is persistent and unexplained.
PAN is a systemic vasculitis affecting medium-sized arteries, potentially impacting various organ systems. Gastrointestinal (GI) involvement is a well-recognized manifestation of PAN, often leading to abdominal pain. However, isolated or initial presentation of PAN primarily as right upper quadrant pain, mimicking more common conditions, can pose a diagnostic dilemma. Understanding this atypical presentation is crucial for timely diagnosis and intervention, as prompt treatment significantly impacts patient outcomes.
Atypical Presentation of PAN: Focus on Right Upper Quadrant Pain
In cases of PAN with gastrointestinal involvement, the mesenteric and hepatic arteries are frequently affected. Angiographic findings often reveal characteristic features such as arterial caliber irregularities, “corkscrew” appearance of vessels, and the presence of distal microaneurysms. While abdominal pain is a common symptom in PAN, with a significant proportion of patients progressing to acute abdomen, right upper quadrant pain specifically has been documented as the primary presenting symptom in several reports.
This presentation can be attributed to the involvement of the hepatic vasculature, which can affect arteries supplying the bile ducts, gallbladder, and liver itself. Such involvement can lead to conditions like acalculous cholecystitis, gallbladder infarcts, hepatic aneurysms, and intrahepatic hematomas or infarcts, all capable of generating right upper quadrant pain. Interestingly, some cases of PAN presenting as RUQ pain are initially misdiagnosed as acalculous cholecystitis, with the diagnosis of PAN only being established after cholecystectomy through tissue analysis. Furthermore, rupture of hepatic aneurysms, a serious complication of PAN, can also manifest as acute right upper quadrant pain.
Navigating the Differential Diagnosis and Considering PAN
The differential diagnosis of right upper quadrant pain is extensive. It commonly includes biliary colic, acute cholecystitis, cholangitis, hepatitis, liver abscess, peptic ulcer disease, pancreatitis, and referred pain from pulmonary or cardiac conditions. In the context of vasculitis, ANCA-associated vasculitides and vasculitis secondary to autoimmune connective tissue diseases might also be considered, though these typically present with broader systemic manifestations.
A diagnostic challenge arises when patients present with RUQ pain and atypical serological findings. While classic PAN is typically associated with certain serological markers, atypical autoantibodies such as p-ANCA, ANA, and anti-Ro antibodies have been observed in some PAN cases. The presence of these antibodies can initially mislead clinicians towards ANCA-associated vasculitides or connective tissue disease-related vasculitis. However, the absence of other characteristic clinical features of these conditions, such as respiratory symptoms, glomerulonephritis, arthritis, skin lesions, or sicca symptoms, should prompt consideration of alternative diagnoses, including PAN. In such scenarios, particularly with persistent and unexplained RUQ pain, angiography becomes a crucial diagnostic tool to assess for the vascular abnormalities characteristic of PAN in the mesenteric and hepatic arterial territories.
Importance of Early Diagnosis and Prompt Treatment in PAN
Delayed diagnosis and treatment of PAN, especially when presenting with gastrointestinal involvement, can lead to severe complications and increased mortality. Vasculitic complications, particularly those related to GI involvement such as bowel infarction or ruptured aneurysms, are major contributors to mortality in the first year after diagnosis. Conversely, early initiation of immunosuppressive therapy, typically with corticosteroids and cyclophosphamide, has been shown to significantly improve outcomes. Prompt treatment reduces the risk of aneurysm formation, decreases associated comorbidities, and lowers mortality rates compared to delayed intervention. Therefore, maintaining a high index of suspicion for PAN in patients with unexplained right upper quadrant pain, particularly when intractable despite initial therapies, is paramount.
Conclusion
While Polyarteritis Nodosa is not a common cause of right upper quadrant pain, it represents a critical consideration in the differential diagnosis, especially in cases with persistent, unexplained pain or when atypical features are present. Clinicians should be aware of the potential for PAN to present primarily with RUQ pain, mimicking more common conditions. A thorough diagnostic approach, including appropriate imaging such as angiography, is essential to identify PAN in a timely manner. Early diagnosis and prompt initiation of immunosuppressive treatment are crucial for preventing disease progression, reducing the risk of life-threatening complications, and improving overall patient outcomes in PAN presenting with gastrointestinal involvement and right upper quadrant pain.
Learning Points
- Polyarteritis nodosa (PAN) is a necrotizing vasculitis affecting medium and small vessels that can involve multiple organs.
- PAN can, in rare instances, primarily or initially affect a single organ system, including the gastrointestinal system.
- PAN should be considered in the differential diagnosis of right upper abdominal pain, particularly in patients with intractable pain.
- Early diagnosis and treatment are crucial to reduce morbidity and mortality in PAN patients presenting with gastrointestinal involvement.
