Polycystic Kidney Disease: An Overview of Information

Polycystic kidney disease is one of the most severe anomalies, characterized by the replacement of a significant part of the renal parenchyma with multiple cysts of various shapes and sizes. Polycystic kidney is attributed to congenital hereditary diseases of the urinary tract.

A characteristic feature of the disease of polycystic kidneys is the presence on the surface of the organs and in their parenchyma of a number of cysts containing a watery (sometimes jelly-like) yellowish liquid with an admixture of blood and pus.

[1], [2], [3]

Epidemiology

In frequency, the anomaly is second only to simple cysts, and the severity of the clinical course and the number of complications ranks first among all renal diseases. Polycystic kidney, according to the literature, among renal diseases is from 0.17 to 16.5%.

The kidneys increase as the functioning parenchyma decreases. Cysts are the enlarged parts of the renal glomeruli and tubules, keeping in touch with the rest of the nephron.

There are two types of polycystosis:

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

Polycystic kidney disease in adults occurs in one in 1,000 people, slowly progressing. The average life expectancy for this disease is 50 years. Manifestations of the disease begin at a young or middle age, and about 10 years it remains compensated. In this stage of the disease, surgical treatment is possible, consisting in opening the cystic formations by resection of their canopy. In recent goals, puncture is used under ultrasound control of the largest cysts, as well as cysts that significantly impair blood flow. Approximately one third of patients have cysts of the liver that do not have functional consequences.

MSCT and MRI can not only detect the cystic structures themselves, but also determine the nature of their contents, helping to differentiate the diagnosis of suppuration of cysts with destruction of the parenchyma. The information obtained can be useful in choosing the tactics of treatment.

[4], [5], [6], [7], [8], [9], [10]

Causes of the polycystic kidney disease

CT. Zakharyan (1937.1941). And then A. Puigvert (1963) formulated the provisions on the unity of the origin of developmental malformations and the medullary layer. Two main groups of anomalies were identified:

• dizembrioplasia of calyces (diverticula of pelvis and calyxes, parapelvic cysts);
• dysembryoplasia of the Malpighian pyramids (megacalix, medullary cystic disease).

Some researchers of the field understand the concept of the "diverticulum of the cup-and-pelvis system" as all pathological retentional changes in the calyxes that have arisen both as a result of the breakdown of the neuromuscular apparatus of the papillary zone, and because of the pressure of its neck with a vessel or scar-sclerotic process in the renal sinus. Others clearly distinguish between the concept of a "congenital" or "true" diverticulum of the cup-and-pelvic system from all types of peri-lateral cystic formations with a closed cavity, as well as retentional changes in the cups into which the renal papillae enter. The embryonic morphogenesis of the diverticulum of the cup-and-pelvic system is revealed as a result of embryological studies, which established that its formation is associated with the absence of the inducing action of the methanephrosis duct on the metanephrogenic blastema.

As a result, a cavity is formed, communicating with the cup-and-pelvic system through a narrow passage, but delimited from the kidney structures. The fundamental difference between a true diverticulum and a false diverticulum is the absence of a renal papilla. The diverticulum of the cup-and-pelvis system is a rounded cavity covered with urothelium, connected with the cup-and-pelvis system by a thin course, into which the renal papilla does not flow. The urine flows into the cavity of the diverticulum on a thin course, stagnating in it. Therefore, in half of the observations, the diverticula of the cup-and-pelvis system contain concretions.

[11], [12], [13]

Symptoms of the polycystic kidney disease

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

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

Polycystic children occur in one of 10,000 newborns. Not only both kidney structures are affected, but also the liver. Very often at birth, hypoplasia of the lungs is noted. Manifestation in childhood is characterized by renal insufficiency, and in adolescent - portal hypertension. The outlook is unfavorable.

Cortical cystic lesions are the most common developmental defect. These include anomalies of the structure, such as multicystosis, polycystosis and, according to earlier ideas, a solitary cyst. At present, a reliable association of the origin of cystic formations with age has been proved. Their innate origin is extremely rare. Combines multicystosis and polycystosis with a common embryo-fetal morphogenesis: the primary tubules of the metanephrogenic blastema do not connect to the methanephros flow. This theory explains to a lesser extent the emergence of solitary cysts. More suitable genesis of renal cysts is retention-inflammatory (result of obstruction and inflammation of the tubular and urinary tract) and proliferative-neoplastic (a consequence of excessive proliferation of the renal epithelium). In connection with this, it is doubtful for us to classify the cysts of the renal parenchyma to developmental anomalies.

The multicystic kidney is a cortical lesion in which practically all nephrons are not connected to the collecting tubules and become retention cysts, while the juxtaglomerular apparatus is absent or sharply underdeveloped. With multicystosis, almost all of the kidney is represented by cystic lesions. Their shells can be calcified. The contents of the cysts are partially reabsorbed glomerular filtrate. The kidney does not function. This defect is very rare - 1.1%. Clinically, it can manifest blunt aching pain in the lumbar region, arterial hypertension. Diagnosis for today is not difficult. Any of the radiation diagnostic methods allows you to establish a diagnosis. Bilateral multicystosis is incompatible with life.

Diagnostics of the polycystic kidney disease

Diagnosis of polycystic kidney is possible with excretory urography, retrograde pyelography, more precisely the diagnosis is established with the help of MSCT, which allows not only to detect an anomaly, but also to present intrarenal relationships, to estimate the width and extent of the cervix, which is necessary for choosing the tactics of treatment. For diverticula among all renal vices - 0,96%. Multiple diverticula are quite rare, and in a third of cases it is the diverticula of the pelvis, and in other cases - the calyx. Calculiosis diverticulum noted in 78% of observations.

The multistage MSCT allows to determine the migration of concrements in the lumen of the diverticulum. This makes it possible to carry out differential diagnostics with calcification of the wall of cystic education. The advantage of MSCT in the diagnosis of the diverticula of the bowl-and-pelvis system is the possibility of detecting them even in the narrow neck of the diverticulum (in case of urography, the contrast material is difficult to penetrate into their lumen, so they are poorly contrasted).

[14], [15], [16], [17], [18]

Treatment of the polycystic kidney disease

The flow of even diverticula complicated by calculus is usually asymptomatic and does not require treatment. If necessary (pyelonephritis attacks), polycystic kidney disease is treated with surgical techniques - percutaneous nephrolithotripsy with fulguration of stroke. The use of remote shock wave lithotripsy has no prospects.

The reckoning of parapelvic cysts for congenital conditions is doubtful today because of their absence in persons younger than 30 years. Therefore, the appearance of parapelvic cystic formations can be explained by the atresia of the lymphatic vessels of the renal sinus, which was proved by morphological studies. The hypothesis of A.V. Ayvazyan and AM Voino-Yasenetsky, explaining the occurrence of renal sinus cysts by the complete cleavage of one of the branches of the cranial end of the methanephros flow from the metanephrogenic blastema.