Primary renal tubular dysgenesis is a very rare familial disorder characterized by incompletely or abnormally developed cortical tubules. Secondary renal tubular dysgenesis is seen in infants born of women who had taken angiotensin-converting enzyme (ACE) inhibitors during pregnancy. Prognosis is poor.
Primitive Renal Tubule Syndrome.
First described by J. E. Allanson in 1992.
Rare, but possibly underdiagnosed. Around 150 cases in 50 affected families reported.
Autosomal recessive inheritance.
Primary renal tubular dysgenesis is linked to mutations in the genes encoding several components of the renin-angiotensin system: AGT, REN, ACE, and AGTR1. Histological changes suggest ischemia or hypoperfusion of renal parenchyma with resultant hypoxia affecting those organs requiring a high oxygen tension for normal growth as a cause for the renal tubular dysgenesis. Secondary renal tubular dysgenesis has been described in twin-to-twin transfusion syndrome, fetal exposure to ACE inhibitors/angiotensin receptor antagonists, and congenital hemochromatosis.
Nephromegaly with characteristic histological appearance whereby the cortical tubules lack normal features of the proximal or distal convolutions. The tubules are short and straight, primitive, and reminiscent of collecting tubules. The glomeruli are crowded with the medullary pyramids smaller than usual. Late second-trimester sonographic demonstration of oligohydramnios, with structurally normal kidneys, should suggest the diagnosis. Associated skull abnormalities may help in suggesting the diagnosis.
Severe persistent oligohydramnios leads to fetal compression and immobility, resulting in the Potter sequence, typified by facial anomalies, redundant skin, limb positioning defects, and lung hypoplasia. Liveborns are anuric and develop renal failure. A number of the affected children have skull abnormalities (calvarial hypoplasia, microcephaly, underdeveloped cranial bones, or widely patent fontanelles) with characteristic Potter facies. Hypotonia may occur. Most patients die in utero during the third trimester or soon after birth from respiratory failure and nonresponsive circulatory failure. Survival is possible with significant chronic renal disease.
Precautions before anesthesia
No details of anesthetic management are available. Assess intravascular volume and electrolyte imbalances, especially potassium. Correct all anomalies preoperatively. Systematic review of cardiovascular and respiratory status (clinical, ECG, chest radiographs, echocardiography, arterial blood gas analysis). Investigations: Full blood count (FBC) (note severity of anemia), clotting times, urea, creatinine, and electrolytes, liver function tests. The effects of sedative drugs for premedication may be unpredictable because of the changes in plasma protein levels and the altered pH.
Fluid balance and electrolytes should be monitored carefully. The use of a regional anesthetic technique may be considered, provided there is no coagulopathy or thrombocytopenia. Postoperative ventilatory support can be necessary in case of respiratory failure.