Kidney diabetes insipidus

Kidney diabetes insipidus . Etiology and pathogenesis. Hereditary disease, in which the kidneys are not capable of producing urine with a higher osmolar concentration than the osmolality of the glomerular ultrafiltrate of the plasma, which is associated with a loss of sensitivity of the renal tubules to the antidiuretic hormone (ADH). Nephrogenic diabetes insipidus should be distinguished from neurohypophysis, in which kidney reactions to ADH are preserved, but the processes of hypothalamic neurosecretion are disrupted.

In nephrogenic diabetes insipidus, the homeostatic function of the kidneys is significantly impaired, aimed at maintaining the water-salt balance. This leads to significant fluctuations in the osmotic pressure of the blood plasma and hyperelectrolithy: the concentration of sodium in the plasma can be increased to 180 meq / l, chlorine up to 160 meq / l. Especially large are these fluctuations in young children, in whom a sense of thirst is not developed. Loss of significant amounts of water leads to the development of dehydration, toxicosis.

Clinical picture. The disease manifests itself in the 3rd-6th month of life with copious diuresis, vomiting, propensity to constipation, feverish condition. Feeling of thirst may be absent. The volume of daily urine of an infant can reach 2 liters, at an older age 5-10 liters.

There is a "salt fever", convulsive conditions are possible. Persistent violations of water-salt balance can lead to the development of hypotrophy, physical retardation, and in some children and mental development. With sufficient introduction of a liquid, this is not observed.

In older children, the state of dehydration develops rarely, the loss of fluid is compensated by its intake and the overall osmolarity of the plasma is maintained within normal limits. The parameters of glomerular renal filtration, excretion of phosphates, amino acids, glucose, as a rule, also do not go beyond the norm. There are cases of a peculiar form of the disease: sensitivity to ADH is absent only at night, but is restored by day. For diagnosis, kidney biopsy is necessary. Microdissection shows a significant (half) shortening of the proximal part of the nephron tubules. At a histological examination it is necessary to distinguish this condition from nephronophytosis, chronic hypokalemia, idiopathic hypercalciuria, cystinosis.

Diagnosis and differential diagnosis. Functional research allows you to clarify the diagnosis of the disease. The sample for urine concentration is based on the exclusion of water intake for 12 hours (for children it is better to use a night break for this purpose, for example, from 19 pm to 7 am). Conducting this sample is permissible only in doubtful cases, since with obvious diabetes insipidus it is unsafe. In healthy children, the osmolar concentration of urine rises to 1000 mosm / l, the osmotic concentration coefficient exceeds 2.5. In diabetes insipidus, the osmolarity of the urine corresponds approximately to the osmolality of the plasma, the osmotic coefficient is about 1; The introduction of ADH is accompanied by a decrease in diuresis and an increase in the osmolarity of the urine. At a nephrogenic diabetes reactions on introduction ADH are completely absent.

ADH is given in / m in a single dose of 3 to 8 units, depending on the age. Too high doses can lead to a distortion of the results of the study due to spasm of the kidney vessels. For setting the sample, pituitrin for injection can be used, containing in 1 ml 5 ED. Children under 1 year are injected with 0.1-0.15 ml, 2-5 years with 0.2-0.4 ml, 6-12 with-0.4-0.6 ml. After the / m administration of pituitrin, several one-hour portions of urine (3-5 h) are collected and its relative density is measured. In normal and with neurohypophysial diabetes, the amount of excreted urine decreases significantly, and its relative density increases significantly, with renal diabetes insipidus the reaction is absent. Differential diagnosis of diabetes insipidus is not particularly difficult. In addition to neurohypophysis non-sugar diabetes it is necessary to bear in mind polyuria, which develops in patients with diabetes mellitus as a consequence of osmotic diuresis.

Treatment of renal diabetes insipidus is symptomatic and is mainly aimed at maintaining water-salt balance by introducing sufficient amounts of liquid. If the child refuses to take the liquid, and also when the signs of dehydration develop, the fluid is injected intravenously into the drip, with a 5% glucose solution being used more often.

Paradoxical effects on renal water transport in this disease have sulfonamide diuretics: administration of hypothiazide at a dose of 25-100 mg per day is accompanied by a significant decrease in diuresis. The antidiuretic effect of these drugs persists for some time and after their cancellation, provided a significant restriction of table salt in the diet. In the treatment of hypothiazide should provide constant monitoring of the indicators of acid-base balance of blood, as well as the content of potassium in the plasma.

In connection with the possibility of developing hypertonic dehydration, febrile illness, moving to areas with a hot climate, surgical interventions are a serious danger for patients, especially young children.

The forecast is relatively favorable.

Prophylaxis is medical genetic counseling.