Stones in the urinary tract

Stones in the urinary tract vary greatly in their prevalence. For example, they are common in North India and the Sudan, but are rare in East and Central Africa. In the ''stone belts' of South East Asia and South America, they are very common, even in children. You should be able to: (1) Relieve the excruciating pain of renal colic. (2) Do a nephrostomy for calculous anuria[md]this can be life-saving, but is rarely needed (23.13). (3) Remove a ureteric stone (23.14). (4) Remove an adult's (23.15) or a child's (23.16) bladder stone. (5) Remove a stone impacted in a child's urethra (23.17). Removing a stone from anyone's kidney, or his renal pelvis, is too difficult to be described here.

Stones are of two kinds: (1) Primary or metabolic stones. (2) Secondary stones resulting from obstruction, or repeated infection. Primary stones are most common in men between 30 and 50, and usually form in the renal pelvis; the lower calyx is the next most common site.

The size and position of a stone determines what it does. If it is small, and remains in the periphery of the kidney, or in a calyx, it may cause few symptoms; if it enlarges it may obstruct part of the kidney. A small stone may pass down the ureter, cause acute renal or ureteric colic as it does so, and later be voided in his urine. If it is too big to do this, it may obstruct the upper end of the ureter, and cause a hydronephrosis which will ultimately destroy the kidney.

Stones in the bladder don't usually return when you remove them, but those in the upper urinary tract often do. ''A gram of prevention is worth a kilo of pills, or a megatonne of surgery'', so warn a patient with a stone in his upper urinary tract that he has about a 50% chance of getting another one during the next 10 years. Advise him according to the instructions below. The most useful preventive measure is a high fluid intake.

Most stones are radio-opaque, so learn where to look for them; an occasional exception is a urate stone in a child's bladder, but even these usually contain enough calcium to let you see them on an X-ray film.

URINARY STONES SPECIAL TESTS. The presence of microscopic haematuria is the most useful test. If there are pus cells, or a patient's urine is alkaline, it is infected.

X-RAYS. Take a plain film of his kidneys, ureters and bladder (a ''KUB'). You can easily miss a stone if: (1) the film is poor, (2) it is only moderately radio-opaque, or (3) it is obscured by bone. Look for kidney stones opposite his second lumbar vertebra. For ureteric stones, see Section 23.14. Don't mistake a gallstone, or a calcified lymph node, for a urinary stone. They are easily distinguished. In a lateral X-ray of his abdomen gallstones are anterior and renal,,, and ureteric stones overlie his lumbar spine.

An intravenous urogram: (1) Will tell you if his kidney has stopped functioning or not. If no contrast medium is excreted, it has stopped functioning, or is excreting so little dye that this is invisible. (2) May help you to find the site of an obstructing stone that is not be visible on a plain film. Take films at 1, 3, 12 and even 24 hours. Enough contrast medium may have accumulated to show up his urinary tract, down to the site of the obstruction.

If contrast medium is concentrated in his kidney (a ''nephrogram'), but does not show up in his renal pelvis, a stone may have blocked its pelviureteric junction, and caused the contrast medium to be retained in his kidney tissue. This is a hopeful sign, because it shows that he still has good renal function.

DIFFERENTIAL DIAGNOSIS. The simplest situation is the patient with colic and a stone in his ureter, described in Section 23.14. Here are some other possibilities:

If he has moderate pain in his costovertebal angle, a high fever, chills, an obviously infected urine, and an intravenous urogram shows that his renal pelvis and calyces are normal, he has acute pyelonephritis.

If he has a palpable tender renal mass, he probably has a hydronephros. If in addition he has fever, toxaemia, and leucocytosis, it is probably a pyonephros.

If he has a dull ache, with occasional fever and pyuria, suspect that he has a stone which is not obstructing his urinary tract.

If he has anuria and renal failure, this can be due to stones on both sides, but it is more likely to be due to chronic interstitial nephritis or pyelonephritis.

CAUTION ! Some stones cause no symptoms, even when they are large.

TREATMENT [s7]FOR URINARY STONES If he has a stone in his ureter, see Section 23.14.

If he has a small kidney stone ([lt]0.5 cm), which is peripheral in his kidney, and is causing no symptoms and no infection, leave it, but watch it carefully, to see if it moves into his renal pelvis and obstructs this.

If it is obstructing his renal pelvis, it should be removed. The risk of hydro- or pyonephros is too high to leave it. If he has stones on both sides, the side with the better function should be operated on first.

If he has renal colic for few days, after which he gradually becomes oliguric, and then anuric, he probably has calculous anuria (23.13). This can arise from bilateral obstruction, or, more commonly, from the obstruction of a single kidney. Catheterization of his bladder produces no urine. A plain film confirms the diagnosis. His blood urea rises. The episode may relieve itself spontaneously as the result of the oedema in his ureter settling, and the infection being brought under control. Watch him for 24 to 48 hours.

If you have a cystoscope and can pass a ureteric catheter, it may slide past the stone; you can then leave it in place for 2 or 3 days, which will relieve the acute situation, perhaps for long enough for you to refer him. Or the catheter may dislodge the stone back into his renal pelvis.

If he does not rapidly improve, you will have to do an urgent nephrostomy (23.13), and refer him.

TO PREVENT RECURRENT STONES ask him to take plenty of fluids. If he has an associated infection, treat it.

If he has a uric acid stone try to raise the pH of his urine. Make it alkaline with sodium bicarbonate tablets three times a day, or potassium citrate mixture 20 ml three times a day. If possible, measure his serum uric acid. Only give him allopurinol if he has recurrent uric acid stones.

If his serum calcium is consistently high, it suggests a parathyroid adenoma, or some other generalized disease. A raised urinary calcium is more common; advise him to restrict his intake of dairy products.

Fig. 23-16 NEPHROSTOMY, ONE[md]EXPOSING THE KIDNEY. A, the incision over the patient's 12th rib. B, he is ready for surgery, with sandbags under his loin and his arm supported. C, latissimus dorsi has been cut and the periosteum is being stripped over his 12th rib. D, and E, removing his rib. F, his rib removed, and his perirenal fat exposed. Alternatively, make an incision just below his 12th rib and don't remove it.