Chapter 33 - Disorders of Renal Function

• normal arrangement of tissue and the amount of tissue are critical for renal functioning in newborns
• the most common congenital anomalies are anomalies in shape and position (e.g., horseshoe kidney = fusion of two kidneys)
• disorders involving a decrease in renal mass (e.g., agenesis, hypogenesis) and a change in renal structure (e.g., renal cysts) are less common congenital anomalies
• dysgenesis is the failure of an organ to develop normally
• agenesis is the complete failure of an organ to develop
• in unilateral renal agenesis, one kidney is absent and the other kidney undergoes hypertrophy to compensate
• Potter syndrome involves characteristic features of newborns with renal agenesis
• in newborns with Potter syndrome, the eyes are widely separated and have epicanthic folds
• in newborns with Potter syndrome, the ears are low set, the nose is broad and flat, the chin is receding, and limb defects are often present
• causes of neonatal renal failure with Potter phenotype:

  • cystic renal dysplasia
  • obstructive uropathy
  • autosomal recessive polycystic disease
  • unilateral agenesis
• hypoplasia is the failure of an organ to reach normal size
• cystic disease involves fluid-filled sacs or segments of a dilated nephron
• tubular obstructions that increase tubular pressure can cause cystic disease
• changes in the basement membrane of the renal tubules that predispose to cystic dilation can cause cystic disease
• the causative factor in cystic disease may be congenital, genetic, or result as a secondary pathology
• replacement of kidney tissue by cysts reduces/removes functional properties and can cause cystic disease
• types of cystic disease of the kidney:

  • simple and acquired renal cysts
  • medullary cystic disease
  • polycystic kidney disease
  • autosomal recessive polycystic kidney disease
• PKD is caused by single gene disorders
• autosomal dominant PKD is the most common renal cystic disease in adults
• manifestations of autosomal dominant PKD:

  • pain
  • gross hematuria
  • infected cysts
  • hypertension due to compression of intrarenal blood vessels
  • activation of renin-angiotensin mechanism
• the progress of autosomal dominant PKD is slow and end-stage is uncommon before 40 years
• autosomal recessive PKD is rare and usually found in infants
• manifestations of autosomal recessive PKD:

  • bilateral flank masses
  • severe renal failure
  • impaired lung development
  • liver fibrosis
  • portal hypertension
• causes of urinary tract obstructions:

  • developmental defects
  • calculi
  • pregnancy
  • benign prostatic hyperplasia
  • scar tissue resulting from infection and inflammation
  • tumours
  • neurologic disorders (e.g., spinal injury)
• manifestations of urinary tract obstructions depend on the site and cause of obstruction and the rapidity with which the condition developed
• common symptoms of urinary tract obstructions:

  • pain
  • signs and symptoms of UTI
  • manifestations of renal dysfunction
• damaging effects of urinary tract obstructions:

  • hydronephrosis
  • stasis of urine
  • development of backpressure
• hydronephrosis is urine-filled dilation of the renal pelvis and calices associated with progressive atrophy of the kidney due to an obstruction of urine outflow
• stasis of urine predisposes to infection and stone formation
• development of backpressure interferes with renal blood flow and destroys kidney tissue while inducing the formation of cysts
• nephrolithiasis is kidney stones (renal calculi)
• kidney stones are crystalline structures that form from components of urine
• requirements for formation of kidney stones:

  • a nidus to form
  • a urinary environment that supports continued crystallization of stone components
  • basic concept of saturation and precipitation in solution
• when a patient has high levels of circulating calcium, it can become very concentrated in the filtrate and, under acidic conditions, that filtrate will undergo precipitation of the calcium and crystals will form, thus a stone is formed
• factors influencing the formation of kidney stones:

  • the concentration of stone components in urine
  • the ability of stone components to complex and form stones
  • the presence of substances that inhibit stone formation
• types of kidney stones:

  • calcium stones (oxalate or phosphate)
  • magnesium ammonium phosphate stones
  • uric acid stones
  • crystine stones
• diagnosis of kidney stones:

  • urinalysis
  • radiography
  • IV pyelography
  • ultrasonography
• preventive treatment for kidney stones:

  • dietary restriction
  • calcium salt supplementation
  • thiazide diuretics
  • cellulose phosphate
• treatment for kidney stones usually involves medications for pain and antibiotics for infection
• techniques for kidney stone removal:

  • ureteroscopic removal
  • percutaneous removal
  • extracorporeal lithotripsy