Polycystic Kidney Disease - Information Overview

Polycystic kidney disease is one of the most severe anomalies characterized by the replacement of a significant portion of the renal parenchyma with multiple cysts of various shapes and sizes. Polycystic kidney disease is classified as a congenital hereditary disease of the urinary tract.

A characteristic feature of polycystic kidney disease is the presence on the surface of the organs and in their parenchyma of multiple cysts containing a watery (sometimes jelly-like) yellowish fluid mixed with blood and pus.

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Epidemiology

In terms of frequency, the anomaly is second only to simple cysts, and in terms of severity of the clinical course and number of complications, it ranks first among all kidney diseases. According to literature, polycystic kidney disease accounts for 0.17 to 16.5% of kidney diseases.

The kidneys enlarge with a decrease in the functioning parenchyma. Cysts are dilated portions of the renal glomeruli and tubules, maintaining a connection with the remaining part of the nephron.

There are two types of polycystic disease:

• autosomal dominant disease (polycystic kidney disease in adults);
• autosomal recessive disease (polycystic kidney disease in children).

Adult polycystic kidney disease occurs in one out of 1000 people, progresses slowly. The average life expectancy for this disease is 50 years. The manifestations of the disease begin in young or middle age, and it remains compensated for about 10 years. At this stage of the disease, surgical treatment is possible, consisting of opening cystic formations by resecting their dome. In recent years, puncture under ultrasound control of the largest cysts, as well as cysts that significantly disrupt blood flow, has been used. About a third of patients have liver cysts, which have no functional consequences.

MSCT and MRI are capable of not only detecting cystic formations themselves, but also determining the nature of their contents, helping in differential diagnostics of cyst suppuration with parenchyma destruction. The information obtained may be useful in choosing treatment tactics.

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Causes polycystic kidney disease

ST. Zakharyan (1937-1941) and then A. Puigvert (1963) formulated provisions on the unity of origin of developmental defects of the CLS and the medullary layer. Two main groups of anomalies were identified:

• dysembryoplasia of the calyces (diverticula of the renal pelvis and calyces, parapelvic cysts);
• dysembryoplasia of the malpighian pyramids (megacalyx, medullary cystic disease).

Some researchers understand the term "diverticulum of the renal pelvis-calyceal system" to mean all pathological retention changes in the calyces that arise as a result of both a disorder of the neuromuscular apparatus of the papillary-pelvic zone and pressure on its neck by a vessel or a cicatricial-sclerotic process in the renal sinus. Others clearly distinguish the term "congenital" or "true" diverticulum of the renal pelvis-calyceal system from all types of peripelvic cystic formations with a closed cavity, as well as retention changes in the calyces into which the renal papillae flow. Embryonic morphogenesis of diverticulum of the renal pelvis-calyceal system was revealed as a result of embryological studies that established that its formation is associated with the absence of the inducing effect of the metanephric duct on the metanephrogenic blastema.

As a result, a cavity is formed that communicates with the renal pelvis-calyceal system through a narrow passage, but is separated from the renal structures. The fundamental difference between a true diverticulum and a false one is the absence of a renal papilla. A diverticulum of the renal pelvis-calyceal system is a round cavity covered with urothelium, connected to the renal pelvis-calyceal system by a thin passage, into which the renal papilla does not flow. Urine flows into the diverticulum cavity through a thin passage, stagnating in it. Therefore, in half of the observations, diverticula of the renal pelvis-calyceal system contain stones.

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Symptoms polycystic kidney disease

Symptoms of polycystic kidney disease are associated either with the cysts themselves (arterial hypertension in 50% of patients, dull aching pain in the lumbar region, hematuria, pyuria) or with manifestations of renal failure. Diagnosis of polycystic disease is not difficult today. Ultrasound in combination with Dopplerography allows not only to identify the disease, but also to clarify the state of renal blood flow.

Most patients die from chronic renal failure, and 10% from cerebral hemorrhage. Treatment of azotemia (including hemodialysis, organ transplantation), pyelonephritis and arterial hypertension can significantly prolong the life of patients.

Polycystic disease in children occurs in one out of 10,000 newborns. Not only both renal structures are affected, but also the liver. Very often, hypoplasia of the lungs is noted at birth. Manifestation in childhood is characterized by renal failure, and in adolescence - portal hypertension. The prognosis is unfavorable.

Cortical cystic lesions are the most common developmental defect. They include such structural anomalies as multicystic disease, polycystic disease and, according to earlier ideas, solitary cyst. Currently, a reliable association between the occurrence of cystic formations and age has been proven. Their congenital origin is extremely rare. Multicystic disease and polycystic disease have in common embryofetal morphogenesis: the primary tubules of the metanephrogenic blastema do not connect with the metanephros duct. This theory explains the occurrence of solitary cysts to a lesser extent. The genesis of renal cysts is more suitable: retention-inflammatory (the result of obstruction and inflammation of the tubular and urinary tract) and proliferative-neoplastic (a consequence of excessive proliferation of the renal epithelium). In this regard, we doubt the classification of renal parenchyma cysts as developmental anomalies.

Multicystic kidney is a cortical cystic lesion in which almost all nephrons have not connected with the collecting ducts and have turned into retention cysts, while the juxtaglomerular apparatus is absent or severely underdeveloped. In multicystic kidney, almost the entire kidney is represented by cystic formations. Their membranes can calcify. The contents of the cysts are partially reabsorbed glomerular filtrate. The kidney does not function. This defect is quite rare - 1.1%. Clinically, it can be manifested by dull aching pain in the lumbar region, arterial hypertension. Diagnostics today is not difficult. Any of the radiological diagnostic methods allows you to establish a diagnosis. Bilateral multicystic kidney disease is incompatible with life.

Diagnostics polycystic kidney disease

Diagnosis of polycystic kidney disease is possible with the help of excretory urography, retrograde pyelography, more accurately the diagnosis is established with the help of MSCT, which allows not only to identify the anomaly, but also to imagine the intrarenal relationships, to estimate the width and length of the neck, which is necessary for choosing the treatment tactics. For diverticula among all renal defects - 0.96%. Multiple diverticula are quite rare, and in a third of cases these are diverticula of the renal pelvis, and in the remaining cases - calyces. Diverticulosis of diverticula is noted in 78% of cases.

Polypositional MSCT allows to determine the migration of stones in the lumen of the diverticulum. This makes it possible to conduct differential diagnostics with calcification of the wall of the cystic formation. The advantage of MSCT in diagnosing diverticula of the renal pelvis and calyces is the possibility of detecting them even with narrow necks of diverticula (during urography, it is difficult for the contrast agent to enter their lumen, so they are poorly contrasted).

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Treatment polycystic kidney disease

The course of even complicated diverticula with calculus is usually asymptomatic and does not require treatment. If necessary (attacks of pyelonephritis), polycystic kidney disease is treated using surgical techniques - percutaneous nephrolithotripsy with fulguration of the course. The use of remote shock wave lithotripsy is futile.

The classification of parapelvic cysts as congenital conditions is currently questionable due to their absence in individuals under 30 years of age. Therefore, the occurrence of parapelvic cystic formations can be explained by atresia of the lymphatic vessels of the renal sinus, which has been proven by morphological studies. The hypothesis of A.V. Ayvazyan and A.M. Voyno-Yasenetsky, explaining the occurrence of renal sinus cysts by complete splitting off of one of the branches of the cranial end of the metanephric duct from the metanephrogenic blastema, seems unrealistic.