Surgical treatment of urinary calculi

Conservative management

Calculi which are smaller than 0.5 cm are likely to pass spontaneously unless they are impacted. Any surgical intervention carries the risk of complication and needless intervention should be avoided. Small renal calculi may cause symptoms by obstructing a calyx or acting as a focus for secondary infection. However, most can be safely observed until they pass.

Preoperative treatment

If urinary infection is present, appropriate antibiotic treatment is started and continued during and after surgery as necessary.

Operation for stone

In developed countries, open surgery for renal calculus disease is uncommon. Most stones are treated by specialist urologists using minimal access and minimally invasive techniques. Open operations are still needed when the appro­priate expertise is not available or newer techniques have failed to clear the calculus. The following account should be read with this in mind.

Modern methods of stone removal

Kidney stones

Percutaneous nephrolithotomy (Fig. 64.25). This involves the placement of a hollow needle into the renal collecting system through the soft tissue of the loin and the renal parenchyma. A wire inserted through the needle is used to guide the passage of a series of dilators which expand the track into the kidney until it is large enough to take the nephroscope used to look for the stone. Small stones may be grasped under vision and extracted whole. Larger stones must be fragmented by an ultrasound or electrohydraulic probe and removed piecemeal.

The aim of the procedure is to remove all fragments if possible and this may take quite a long time if the calculus is large. When the operation is finished a nephrostomy tube is left to drain the system. This decompresses the kidney and allows repeated access to the system if stone particles remain. Percutaneous nephrolithotripsy is sometimes combined with extracorporeal shock-wave lithotripsy (ESWL) in the treatment of complex (stag-horn) calculi. The surgeon removes the central part of the stone percutaneously and the more peripheral fragments are treated by ESWL.

Complications of percutaneous nephrolithotripsy include (1) haemorrhage from the punctured renal parenchyma — this may be profuse and difficult to control; (2) perforation of the collecting system with extravasation of irrigant (which should be saline); (3) perforation of the colon or pleural cavity during placement of the percutaneous track.

Extracorporeal shock-wave lithotripsy. The management of kidney stones has been revolutionised by the development of lithotriptors. The first of these was made in Germany by the Dornier Company. Many machines of different design ate now available.

A urinary calculus is a crystalline structure. If it is bombarded with shock waves of sufficient energy it will disintegrate into fragments. The principle is seen at its simplest in the original Dornier machine where shock waves were generated by an electrical discharge placed at one focus of an ellipsoid mirror. The patient was positioned, under radiographic control, so that the calculus was subjected to the full force of the shock waves where they were concentrated at the second focus of the mirror. As shock waves are poorly transmitted through air, both the patient and the shock-wave generators were immersed in a bath of water.

Modern ESWL machines do not have a water bath; the fluid is confined to the path that the shock waves must follow to reach the kidney. The shocks may be generated by the discharge of an array of piezoelectric cells and they may be aimed by ultrasound rather than X-ray imaging (Fig. 64.26). The devices also differ in the strength of the disruptive force which they can develop. Less powerful machines are less effective in breaking stones and several treatments may be necessary to achieve clearance of a calculus. Weaker shocks hurt less, however, and treatment can be given without general anaesthesia.

When ESWL is successful, the stone fragments have to be passed down the ureter. Ureteric colic is common after ESWL and the patient must be given appropriate analgesia, usually in the form of a nonsteroidal anti inflammatory drug such as diclofenac. If the stone is large the bulky fragments may become impacted in the ureter, causing obstruction. To avoid this, a self-retaining stent should be placed in the ureter so that the kidney can drain while the pieces of stone pass. Occasionally impacted fragments have to be removed ureteroscopically (see below).

1n addition to pain and fragment impaction, the principal complication of ESWL is infection. Many calculi contain bacteria which are released when the stone is broken. It is wise to give prophylactic antibiotics before ESWL and an obstructed system should be decompressed by the insertion of a ureteric stent or percutaneous nephrostomy before treatment.

  The clearance of stone from the kidney will depend upon the consistency of the stone and its site. Most oxalate and phosphate stones fragment well and, if lying in the renal pelvis, will clear within days. The results with harder stones, especially cystine stones, are less satisfactory. When treating

calyceal stones, the patients should be warned that the clearance of fragments may take months.

There is currently great interest in the long-term outcome of patients treated by ESWL. Certainly some stones recur, especially if small fragments remain after treatment. Long-term renal damage now seems unlikely.

Open Surgery for renal calculi (Fig. 64.27)

Operations for kidney stone are usually performed via a loin or lumbar approach. All of the procedures are difficult unless the kidney is fully mobilised and its vascular pedicle controlled. A sling should be placed around the upper ureter to stop stones migrating downwards.

Pyelolithotomy is indicated for stones in the renal pelvis. When the wall of renal pelvis has been dissected free from its surrounding fat, an incision is made in its long axis directly on to the stone. The stone is removed with gallstone forceps, care being taken not to break it because fragments may be difficult to retrieve. Stone fragments in peripheral calyces may be detected by direct palpation or by intraoperative radiography or nephroscopy. If there is no infection, the pelvic incision is closed with interrupted absorbable sutures. If there is gross sepsis, it is wise to place a nephrostomy to drain the system.

Extended pyelolithotomy. The plane between the renal sinus and the wall of the collecting system is developed on the posterior surface of the kidney. This avoids major vessels and allows incisions to be made into the calyces so that even large stag-horn stones can be removed intact.

Nephrolithotomy. If there is a complex calculus branching into the most peripheral calyces, it may be necessary to make incisions into the renal parenchyma to clear the kidney. Nephrolithotomy may also be necessary when the adhesions resulting from previous surgery make access to the renal pelvis difficult. The renal pedicle must be temporarily cross-clamped to reduce bleeding from the highly vascular renal tissue. Incisions are made just posterior and parallel to the most prominent part of the convex renal border where the territories of the anterior and posterior branches of the renal artery meet (Brödel’s line). Cooling the kidney with ice packs or cooling coils extends the time that the kidney can remain ischaemic without permanent damage. All the incisions must be carefully closed with haemostatic sutures and the patient observed after the operation for signs of reactionary haemorrhage.

Partial nephrectomy is sometimes preferable when the stone is present in the lowermost calyx and there is associated infective damage to the adjacent parenchyma.

Nephrectomy is indicated when the kidney has been destroyed by obstruction and infection associated with stone disease. This is particularly the case when there is xanthogranulomatous pyelonephritis. This stone-related inflammatory mass must be removed with particular care because it is liable to be attached to adjacent structures such as the colon.

Treatment of bilateral renal stones. Usually the kidney with better function is treated first, the operation on the contralateral side being deferred for 2—3 months. Exceptions are if either one kidney is more painful, suggesting an obstruction, or there is pyonephrosis in one kidney — this must be drained by percutaneous nephrostomy.

In cases of silent bilateral stag-horn calculi in the elderly and infirm, it may be best not to operate. The patient should be encouraged to maintain a high fluid intake.

Prevention of recurrence

Frčre Jacques, that famous lithotomist of the Middle Ages, used to say, ‘I have removed the stone, but God will cure the patient’. When a renal stone has been removed, steps must be taken to prevent recurrence.

Ideally all stone formers should be investigated to exclude metabolic factors. In practice the pick-up rate in patients with a single small stone is very small. The urine of all patients with stones should be screened for infection. The following investigations are appropriate in bilateral and recurrent stone formers:

serum calcium, measured fasting on three occasions to exclude hyperparathyroidism; serum uric acid;

urinary urate, calcium and phosphate in a 24-hour collection. The urine should also be screened for cystine;

analysis of any stone passed.

  Dietary advice is not usually helpful in avoiding stone recurrence in people who have a normal balanced diet. Those who consume excessive amounts of milk products (calcium stones), rhubarb, strawberries, plums, spinach and asparagus (calcium oxalate stones) should be advised to be more moderate.

Patients with hyperuricaemia should avoid red meats, offal and fish, which are rich in purines and should have treatment with allopurinol. Eggs, meat and fish are high in sulphur-containing proteins and should be restricted in those with cystinuria.

The most effective dietary advice is that originally offered to stone sufferers by Hippocrates. They should drink plenty to keep their urine dilute. Fluid intake should be increased appropriately to take account of increased losses.

Drug treatment has not been shown to be effective other than in those few patients who are shown to have idiopathic hypercalciuria. Bendrofluazide 5 mg and a calcium restricted diet reduces urinary calcium.