How do we diagnose calciphylaxis secondary to steal syndrome in a patient with end-stage renal disease (ESRD)?

Diagnosis of Calciphylaxis Secondary to Steal Syndrome in ESRD Patients

The diagnosis of calciphylaxis secondary to steal syndrome in patients with end-stage renal disease requires a combination of clinical assessment, laboratory testing, and imaging studies, with fluoroscopy fistulography and ultrasound duplex Doppler being the most appropriate initial diagnostic approaches. 1

Clinical Presentation

• Patients typically present with painful skin lesions, tissue necrosis, and ischemic symptoms in the extremity with the dialysis access 2, 3
• Symptoms may include pain, coldness, cyanosis, and necrosis in the affected extremity, particularly in the distal portions 1
• Absence of pulse and thrill on physical examination of the hemodialysis access suggests potential thrombosis that may contribute to steal syndrome 1
• Acronecrosis (gangrene occurring in fingertips and toes) is a characteristic finding in severe cases 1

Diagnostic Approach

Initial Imaging

• Fluoroscopy fistulography and ultrasound duplex Doppler of the hemodialysis access are the first-line imaging modalities for suspected vascular steal syndrome 1
• Both imaging procedures are complementary and should be ordered together to effectively manage the patient's care 1
• Fluoroscopy fistulography with intervention is usually appropriate to treat a patient with clinical suspicion of vascular steal syndrome 1

Ultrasound Findings

• Duplex Doppler ultrasound may demonstrate reversal of blood flow distal to the arterial anastomosis (flow towards the fistula) or bidirectional flow 1
• However, retrograde flow on color Doppler ultrasound evaluation does not reliably predict clinical steal syndrome 1
• Systolic velocity ratio (SVR) measurements can help assess the severity of stenosis 1

Arteriography Findings

• Complete arteriography from the aortic arch to the palmar arch can reveal arterial stenoses that may contribute to peripheral ischemia 1
• Studies have shown that 62% of patients referred for assessment of steal syndrome had hemodynamically significant (>50%) arterial stenosis 1
• Diagnostic fistulography via percutaneous access can support management of dialysis-associated hand ischemia syndrome (DHIS) 1

Laboratory Assessment

• C-reactive protein is the most helpful laboratory test for diagnosing calciphylaxis, reflecting the inflammatory component of the condition 2, 4
• Serum calcium and phosphate levels are not reliably predictive of calciphylaxis and cannot be used alone for diagnosis 3, 4
• Monitoring of proteinuria and/or albuminuria should be considered standard care as it is a risk factor for progression of CKD 1

Confirmatory Testing

• Skin biopsy has significant limitations with variable sensitivity (20-80%) and risk of traumatizing vulnerable tissue 3, 4
• Biopsy may reveal vascular calcification, fibrosis, and thrombosis of small to medium-sized dermal vessels 2
• Non-invasive investigations such as digital/brachial index measurements, transcutaneous oxygen saturation, and digital plethysmography may assist in evaluating patients with symptoms suggestive of arterial steal 1
• A systolic pressure index <0.5 has been associated with abnormal nerve conduction studies with a positive predictive value of 75% 1

Differential Diagnosis

• Coumadin-induced skin necrosis or heparin-induced thrombocytopenia necrosis may present similarly 5
• Calciphylaxis can rarely occur in patients without renal failure or elevated parathyroid hormone levels 6
• Pediatric cases of calciphylaxis in ESRD have been reported, though they are rare 7

Pitfalls and Caveats

• Relying solely on calcium and phosphate levels for diagnosis is inadequate, as calciphylaxis can occur even with normal values 3, 4
• Skin biopsy may be inadequate in 30% of cases and risks traumatizing vulnerable tissue 4
• The demonstration of retrograde flow on ultrasound does not reliably predict clinical steal syndrome 1
• Calciphylaxis has a high mortality rate, making early diagnosis crucial 7, 8
• Radiological findings of superficial vascular calcifications should be used in conjunction with clinical, laboratory, and histopathological data for accurate diagnosis 8