Polycystic kidney disease (PKD) and nephrotic syndrome

POLYCYSTIC KIDNEY DISEASE (PKD)


GENERAL FEATURES


• PKD is a genetic disorder that can exhibit systemic manifestations but primarily affects the kidneys.


• It is caused by a gene defect on either chromosome 4 or 16. The chromosome 16 gene is the more common defect and is characterized by a faster progressing disease. 


• Autosomal dominant PKD 
(ADPKD), the most common form of the disease, affects 1:400 to 1:1,000 persons and is often diagnosed in the fourth decade of life.


• Autosomal recessive PKD manifests in childhood, is associated with poorer outcomes, and is significantly less common than the autosomal dominant form (1 in 20,000 persons affected).


• Fifty percent of patients with PKD will have end-stage renal disease (ESRD) by age 60 years.


• Fifty percent to 80% of patients with PKD will have hypertension.


• Other associated disorders include infected renal cysts/renal abscesses, nephrolithiasis, hepatic cysts, cardiac valvular disease, and intracranial aneurysms (4% of younger patients, 10% of older patients). 


CLINICAL ASSESSMENT 


• History


– Usually patients present in their 20s to 40s with varying signs and symptoms including abdominal or back pain (secondary to large renal cysts), hematuria, recurrent urinary tract infections (UTIs), hypertension, presence of a palpable abdominal mass, or in acute renal failure.


– Often kidney cysts are found incidentally in asymptomatic patients on imaging studies.


– Family history is present in 75% of cases; therefore, a detailed family history is needed with a focus on kidney disorders and intracranial aneurysms.


• Physical examination


– BP screening and monitoring is important given the high incidence of concomitant hypertension with PKD.


– Kidneys may be so large that they are palpable.


• Laboratory/radiology studies


– Urinalysis can show hematuria, proteinuria (usually mild), or signs of UTI. Fat oval bodies are almost pathomneumonic for PKD, being otherwise routinely found only in nephrotic syndrome.


– Abdominal ultrasonography (US) is the test of choice for diagnosis in symptomatic patients and for screening high-risk patients.


– CT or MRI scans can be used as a confirmatory test if the US results are unclear.


– Neuroimaging to screen for intra­cranial aneurysms is controversial and should be reserved for patients with a family history of intracrani­al aneurysm. Depending on the size, the risk of intervention is approximately equal to the risk of bleeding.


– Urography can be beneficial in patients with recalcitrant hematuria or UTIs. With recalcitrant infections, CT urography can help determine if pyelonephritis has progressed to infect the cysts. 


DIAGNOSIS 


• Diagnostic criteria of ADPKD 


– Two kidney cysts on either kidney before age 30 years


– Two kidney cysts in one kidney at age 31 to 59 years


– Four kidney cysts in one kidney after age 60 years


TREATMENT 


• Symptomatic treatment includes adequate pain control, management of renal failure, and strict control of hypertension.


• Patients often have gastroenterologic symptoms from the mass effect of the large kidney cysts.


• Tight BP control can help prevent progression to ESRD.


• Diligent diagnosis and treatment of UTIs are essential. 


• Renal transplant can be a treatment option for management of ESRD. 


• Patients often require bilateral nephrectomy for infection and pain management.