Spongy (medullary) kidney is a congenital multicystic deformity of the renal collecting ducts of the Malpighian pyramids, which gives the kidney tissue the appearance of a porous sponge. In the event of complications (pyelonephritis and nephrocalcinosis), renal colic, pyuria, hematuria are noted. Pathology is diagnosed with retrograde pyelography and excretory urography. Treatment for clinical symptoms is aimed at eliminating negative consequences. If conservative treatment is ineffective, stones are removed from the kidney, nephrostomy, kidney resection, nephrectomy.
Double-sided defect
With spongy kidneys, in most cases there is a bilateral defect in the medullary substance, while cystic disorders of varying severity can partially or completely affect the renal papillae. Unlike polycystic, spongy has a regular shape, smooth surface, smooth contours andsome increase in size compared to the age norm. On the cut, it has an expansion of the renal terminal tubules with many small cysts and cavities in the area of the pyramids.
Sizes
The size of cysts ranges from 1 to 4 mm, increasing towards the center. With a spongy kidney, cystic formations of two types are noted - diverticuloid protrusions into the lumen of the tubules, with a cylindrical epithelium, or closed cavities formed by combining small cysts that are isolated from the renal tubules and lined with squamous epithelium. Cystic cavities often contain a yellowish clear fluid (in the absence of an inflammatory process), calcified calculi, and desquamated cells. Due to leaching, small stones from the tubules may be observed in the calyces or renal pelvis.
Transformation of kidney tissue
Renal tissue in the area of the pyramids in spongy kidneys, as a rule, is fibrous and dense, and with concomitant pyelonephritis, it often has an inflammatory transformation.
Calcification of the parenchyma of such a kidney (nephrocalcinosis) is considered a secondary disorder, since urine stasis in the dilated tubules and cystic cavities contributes to the deposition of calcium s alts. With spongy kidneys, their work is preserved for a long time. And the distortion of the parenchyma can provoke any infectious process, the progression of stone formation processes and changes in the patency of the urinary tract.
Reason for developmentdiseases
Most urological studies confirm that spongy kidneys (according to ICD-10 - Q61), as anomalies of intrauterine development, are similar in pathogenesis and etiology to polycystic kidneys. Scientists also believe that the occurrence of this pathology is associated with a late violation of embryogenesis, and changes in the collecting ducts of the kidneys can also be observed in the postnatal period. The hereditary nature of this disease is confirmed, but the type of inheritance is most often sporadic.
Spongy kidneys are observed mainly in older and middle-aged people, in most cases - in men. Due to the long latent course of the pathological process in childhood, the disease is found relatively rarely.
Symptoms of the disease
Usually, for a long period of time, the pathology is not clinically manifested. Symptoms develop in the age range from 20 to 40 years with the occurrence of various complications: the formation of stones in the cystic cavities, infections of the urinary tract and kidneys. The main clinical manifestations of complicated spongy kidneys are dull or paroxysmal acute pain in the lumbar region, micro- and macrohematuria, pyuria.
Papillary nephrocalcinosis is observed in this pathology in more than 62% of cases. Renal colic occurs as a result of the migration of small stones from the cystic cavities into the pelvis and calyces. The development of the inflammatory process due to the penetration of small stones into the pelvis-calyx system and the violation of the outflowurine can be manifested by a periodic increase in temperature, impaired urination. Rarely, in severe forms of urolithiasis and secondary recurrent infection, purulent fusion and death of the parenchyma may develop, which is manifested by symptoms of renal failure.
Diagnostic measures for this pathology
The diagnosis of spongy kidneys is based on the results of an extensive urological examination, the main method of which is excretory urography. On the urogram, one can see intensely contrasted, fan-shaped and mosaic-shaped cystic pampiniform cavities and expansion of the collecting ducts. Changes in the morphological nature in the spongy kidney usually affect the medullary distal zone of the organ, while the cortical substance and the cortico-medullary zone remain, as a rule, unchanged.
In the cystic cavities located in the papillary zone, the contrast agent for x-rays lingers longer than in the cups, which indicates stasis in the collecting ducts. The development of nephrocalcinosis may be indicated by papillary calculi darkened with radiopaque substances.
Many people wonder if it is possible to see a spongy kidney on an ultrasound. We will talk about this below.
Retrograde pyelography
Somewhat less often, retrograde pyelography is used in the diagnosis of the disease, since it is not always possible to determine changes in the dilated ducts of the kidney on pyelograms. X-ray examinations of the kidneys are advisable to carry out with a combination of spongy kidneys with nephrolithiasis ornephrocalcinosis to detect microliths and calcifications located in the distal pyramids. In this case, the overview images visualize the shadows of small stones in the papillary cysts, partially or completely coinciding with the shadows of the cavities in the excretory urogram.
Is the medullary spongy kidney determined by ultrasound? Ultrasound examination does not always allow to see small cysts in the deep layers of the renal tissues. Additionally, such a diagnostic event allows you to determine the presence of stones, hematuria and pyuria.
Laboratory tests for spongiform kidneys also help detect pyuria, hematuria, mild hypercalciuria, and proteinemia.
Differential diagnosis of this disease is carried out with pathologies in which there is a polycystic lesion of the medullary tissue of the kidneys (polycystic kidney disease, cystic pyelitis, papillary necrosis, chronic pyelonephritis), as well as with nephrocalcinosis, nephrolithiasis, tuberculosis.
See below for a photo of a spongy kidney on ultrasound.
Therapy
Spongy buds - why is it dangerous?
With an uncomplicated pathological process and its asymptomatic course, no therapy, as a rule, is carried out. In this case, the patient is shown preventive measures to reduce the likelihood of complications. With the clinical manifestation of spongy kidneys, treatment is focused on preventing the development of a secondary infection in the urinary tract and metabolic disorders.(subsequent deposition of calcium s alts in cystic-modified tubules of the kidneys). If pyelonephritis occurs, drink plenty of fluids, a low-calcium diet, and prolonged antibiotic therapy.
In order to prevent the formation of an iatrogenic infection, instrumental urological manipulations in patients with spongy kidneys are indicated only in exceptional cases. Nephrostomy is necessary when the pathological process is complicated by pyelonephritis or urolithiasis, as well as in the absence of the effectiveness of traditional treatment. With focal cystic deformities affecting individual segments of the kidneys, they are resected.
Organ removal
Removal of an organ (nephrectomy) is performed extremely rarely and only with one-sided lesion. The migration of small stones, which disrupts the outflow of urine, may be an indication for the prompt removal of stones from the kidneys using nephrolithotomy, pyelolithotomy, percutaneous nephrolithotripsy, remote nephrolithotripsy. In mild cases, the prognosis for spongy kidneys is favorable. However, with the onset and progression of nephrocalcinosis and the addition of a secondary infection, it may worsen over time. With the complete absence of treatment of a complicated process, this leads to the formation of pus in the kidney and further loss of the organ.
