Материал: Oxford American Handbook of Urology ( PDFDrive )

CYSTIC RENAL DISEASE: MEDULLARY SPONGE KIDNEY (MSK) 337

Treatment

Asymptomatic MSK disease requires no treatment. General measures to reduce urine calcium levels help reduce the chance of calcium stone formation (high fluid intake, vegetarian diet, low salt intake, consumption of fruit and citrus fruit juices). Thiazide diuretics may be required for hypercalciuria resistant to dietary measures designed to lower urine calcium concentration.

Intrarenal calculi are often small and, as such, may not require treatment, but if indicated this can take the form of ESWL or flexible ureteroscopy and laser treatment.

Ureteric stones are again usually small and will therefore pass spontaneously in many cases, with a period of observation. Renal function tends to remain stable in the long term.

338 CHAPTER 7 Miscellaneous urological diseases of kidney

Acquired renal cystic disease (ARCD)

Definition and epidemiology

ARCD is cystic degenerative disease of the kidney with greater than 5 cysts visualized on CT scan. By definition, this is an acquired condition, in contrast to adult polycystic kidney disease (ADPKD), which is inherited (in an autosomal dominant fashion). It is predominantly associated with chronic and end-stage renal failure (originally, it was thought to specifically affect patients on hemodialysis).

It is clinically important because it may cause pain or hematuria and is associated with the development of benign and malignant renal tumors.

Approximately one-third of patients develop ARCD after 3 years of dialysis. The male-to-female ratio is 2:1.

Pathology

Usually multiple, bilateral cysts are found mainly within the cortex of small, contracted kidneys. Cysts vary in size (average 0.5–1 cm) and are filled with a clear fluid, which may contain oxalate crystals. They usually have cuboidal and columnar epithelial linings and are in continuity with renal tubules (and thus cannot be defined as simple cysts).

Atypical cysts have a hyperplastic lining of epithelial cells, which may represent a precursor for tumor formation. Renal transplantation can cause regression of cysts in the native kidneys.

Etiology

The exact pathogenesis is unknown, but several theories have been proposed. Obstruction or ischemia of renal tubules may induce cyst formation. Renal failure may predispose to the accumulation of toxic endogenous substances or metabolites that alter the release of growth factors and result in changes in sex steroid production or cause cell proliferation (secondary to immunosuppressive effects) that results in cyst formation.

Associated disorders

There is an increased risk of benign and malignant renal tumors. The chance of developing renal cell carcinoma is 3–6 times greater than that in the general population (males > females).

ARCD may also be associated with tubulointerstitial nephritis and membranoproliferative glomerulonephritis.

Presentation

Flank pain, UTI, macroscopic hematuria, renal colic (stone disease), and hypertension can occur.

Investigation

This depends on the presenting symptoms.

-For suspected UTI—culture urine

-For hematuria—urine cytology, flexible cystoscopy, and renal ultrasound. On ultrasound the kidneys are small and hyperechoic, with multiple cysts of varying size, many of which show calcification. If the nature of the cysts cannot be determined with certainty on ultrasound, arrange for a renal CT.

ACQUIRED RENAL CYSTIC DISEASE (ARCD) 339

Treatment

Persistent macroscopic hematuria can become problematic, exacerbated by heparinization (required for hemodialysis). Options include transfer to peritoneal dialysis, renal embolization, or nephrectomy.

Infected cysts that develop into abscesses require percutaneous or surgical drainage. Radical nephrectomy is indicated for renal masses with features suspicious of malignancy.

Smaller asymptomatic masses require surveillance.

340 CHAPTER 7 Miscellaneous urological diseases of kidney

Autosomal dominant (adult) polycystic kidney disease (ADPKD)

Definition

ADPKD is an autosomal dominant inherited disorder leading to the development of multiple expanding renal parenchymal cysts.

Epidemiology

Incidence is 0.1%; 95% of cases are bilateral. Symptoms manifest in the fourth decade. ADPKD accounts for 10% of all cases of renal failure.

Pathology

The kidneys reach an enormous size due to multiple fluid-filled cysts and can easily be palpated on abdominal examination. Expansion of the cysts results in ischemic atrophy of the surrounding renal parenchyma and obstruction of normal renal tubules.

End-stage renal failure is inevitable and occurs around the age of 50 years.

Associated disorders

These include a 10–30% incidence of Circle of Willis berry aneurysms (associated with subarachnoid hemorrhage); cysts of the liver (33%), pancreas (10%), and spleen (<5%); renal adenoma; cardiac valve abnormalities; aortic aneurysms; and diverticular disease.

Etiology

PKD-1 gene defects (chromosome 16) account for 90% of cases; PKD-2 gene defects (chromosome 4) cause 10%, and now a third gene, PKD-3 is also implicated.

Pathogenesis theories include intrinsic basement membrane abnormalities; tubular epithelial hyperplasia (causing tubular obstruction and basement membrane weakness); and alterations in the supportive extracellular matrix due to defective proteins, all of which may cause cyst formation.

Presentation

Patients have a positive family history (50% inheritance); palpable abdominal masses; flank pain (due to mass effect, infection, stones, or following acute cystic distension due to hemorrhage or obstruction); macroscopic (and microscopic) hematuria; UTI; and hypertension (75%).

Renal failure may present with lethargy, nausea, vomiting, anemia, confusion, and seizures.

Differential diagnosis

This includes renal tumors; simple cysts; von Hippel–Landau syndrome (cerebellar and retinal hemangioblastomas; renal, adrenal, and pancreatic cysts); and tuberous sclerosis (adenoma sebaceum, epilepsy, learning difficulties, with polycystic kidneys and renal tumors).

AUTOSOMAL DOMINANT (ADULT) POLYCYSTIC KIDNEY DISEASE 341

Investigation

This depends on the presenting symptoms.

-For suspected UTI—culture urine

-For hematuria—urine cytology, flexible cystoscopy, and renal ultrasound. On ultrasound the kidneys are small and hyperechoic, with multiple cysts of varying size, many of which show calcification. If the nature of the cysts cannot be determined with certainty on ultrasound, arrange for a renal CT.

-Renal failure will be managed by a nephrologist. Anemia may occur, though ADPKD may cause increased erythropoietin production and polycythemia.

-Renal imaging (ultrasound and CT are useful for investigation of complications)

Treatment

The aim is to preserve renal function as long as possible (control hypertension and UTI). Infected cysts (abscesses) should be drained.

Persistent, heavy hematuria can be controlled by embolization or nephrectomy.

Progressive renal failure requires dialysis and, ultimately, renal transplantation.