RENAL DISORDERS


What are renal calculi?
Commonly also known as kidney stones, medical word-Nephrolithiasis. A common cause of blood in the urine and pain in the abdomen, flank or groin. Occurs in 1 in 20 people at some time in their life and after being cured have a recurrence rate of 50% within five years

Signs and symptoms
The pain is usually of sudden onset, very severe and colicky (intermittent), not improved by changes in position, radiating from the back, down the flank, and into the groin. Nausea and vomiting are common.

How is the diagnosis completed?
An abdominal USG usually shows calculi if present, their size and location can also be seen x-ray might be optionally done.
Stones or obstruction of the ureter may be seen on:

Kidney ultrasound
IVP (intravenous pyelogram )
Abdominal x-rays
Retrograde pyelogram
Abdominal CT scan
Abdominal/kidney MRI
Tests may reveal high levels of calcium in the blood or urine.

Causes
Kidney stones form when there is a decrease in urine volume or an excess of stone-forming substances in the urine. The most common type of kidney stone contains calcium in combination with either oxalate or phosphate. Unusually increased excretion of stone-forming components such as calcium, oxalate, urate, cystine, xanthine, and phosphate may be responsible .

Metabolic abnormalities (a patient may show more than one)
Supersaturation of urine with stone-forming salts
Hypercalciuria (>300 mg/24hr): 40-60% of cases
Hyperuricosuria (>750 mg/24hr): 20-35% of cases
Hyperoxaluria (>40 mg/24hr): 10-20% of cases
Cystinuria (>250 mg/L): 1-2% of cases
Reduced inhibitors of stone formation
Hypocitraturia (<320 mg/day): 10-40% of cases
Hypomagnesuria
Abnormal nephrocalcin, or other glycoprotein defects (Tamm-Horsfall protein, glycosaminoglycan, uropontin, crystal matrix protein)
Infection with urease-producing organisms (mostly Proteus): 10-20% of cases
Alterations in urinary pH
pH<5.5 leads to uric acid stones
pH>7.5 seen with struvite stones

Dehydration through reduced fluid intake or strenuous exercise without adequate fluid replacement increases the risk of kidney stones. Obstruction to the flow of urine can also lead to stone formation. Kidney stones associated with infection in the urinary tract are known as struvite or infection stones.

Men are especially likely to develop kidney stones. The prevalence of kidney stones begins to rise when men reach their 40s and increases as they reach their 70s. People who have already had more than one kidney stone are prone to develop more stones.

A number of different conditions can lead to kidney stones
Gout results in an increased amount of uric acid in the urine and can lead to the formation of uric acid stones.

Hypercalciuria (high calcium in the urine), another inherited condition, causes stones in more than half of cases. In this condition, too much calcium is absorbed from food and excreted into the urine, where it may form calcium phosphate or calcium oxalate stones.

Other conditions associated with an increased risk of kidney stones include:

hyperparathyroidism, kidney diseases such as renal tubular acidosis, and some inherited metabolic conditions including cystinuria and hyperoxaluria.

People with inflammatory bowel disease or who have had an intestinal bypass or ostomy surgery are also more likely to develop kidney stones.

Some medications also raise the risk of kidney stones. These medications include some diuretics, calcium-containing antacids, and the protease inhibitor Crixivan (indinavir), a drug used to treat HIV infection.