General Surgery and Urology – Kidney and Ureter MCQs (Part 3)

Imaging of Ureteric Colic (Calculus)

• A plain film of the abdomen and renal ultrasound examination will diagnose most stones.              • About of 90% of calculi are radiopaque (calcium, cystine).
• Excretory urography is necessary to verify their location within the urinary tract and also affords     a qualitative measure of renal function.
• An acutely obstructed kidney may show only increasing density of renal shadow without                      significant radiopaque material in calices.
• A non-opaque stone (uric acid) will be seen as a radiolucent defect in the opaque contrast media.

Intracorporeal Lithotripsy

Techniques:
• Electro hydrolytic lithotripter (EHL).
− Narrow safety margin, may damage ureteral mucosa but least expensive
− Suitable for bladder calculi.
− Successfully fragments 90% of calculi.
• Ultrasonic lithotripter
• Ballistic lithotripter
• Laser lithotripter (Holmium-YAG lager)
− Ho-YAG is the best laser source for intracorporeal lithotripsy, primarily through a photothermal mechanism that causes stone vaporization.
− Most effective and versatile with good safety margin
− Fragments all stones regardless of composition. It can cut through the metal. So, caution must be exercised while using a basket.
− Potential side effect is production of cyanide when uric acid stones are treated. This has been reported in vitro. The clinical experience has suggested no significant cyanide toxicity.
− Major disadvantage is initial high cost of the device and the laser fibers.

• Prompt drainage of hydronephrosis by ‘J’ stent drainage is the single best option to manage             uremia in this patient with bilateral renal calculi, to allow recovery of renal function at the                 earliest.
• Hemodialysis may be used afterwards if renal recovery is prolonged necessitating removal of           waste products.
• Prompt drainage of hydronephrosis by ‘J’ stent placement is the procedure of choice for                     hydronephrosis complicated with renal failure in the setting of urinary obstruction.
• Prompt drainage of hydronephrosis is indicated of renal function is compromised or urinary             infection (UTI) is suspected, to preserve/salvage renal function.                                                               • Prompt drainage can be achieved by placement of a ureteral sent or through percutaneous                nephrostomy.                                                                                                                                                      • The drainage procedure of choice in emergent situations is cystoscopy with placement of                    internalized double ‘J’ureteral stent. This procedure has the advantage of being a completely internal drainage system.
• Percutaneous nephrostomy may be used to allow urinary drainage if the stone is too impacted to allow passage of a guide wire for sent placement.

Ureteroscopy:                                                                                                                                                     • Ureteroscopic stone extraction is highly efficacious for lower ureteric calculi.
• The use of small-caliber ureteroscopes and the advent of balloon dilatation or ureteral access           sheaths have increased stone-free rates (66%-100%) dramatically.
Indications:
• Lower ureteric calculi.
• Upper ureteric calculi of ESWL failure.
• Suspicion of urothelial tumor (filling defect, Brush cytology).
• Ureteric dilatations or DJ stents.
• Retrieval of foreign body.
Complications:
• Iatrogenic injuries or ureteric perforations.

• PCNL done through the 11th intercostals space traverses the lower aspect of pleura and can               result in significant hydrothorax from large amount of irrigative fluid.

PCNL (Percutaneous Nephrolithotomy):                                                                                                         • Removal of kidney stone via a ‘track’ developed between the surface of the skin and the                      collecting system of the kidney.
• The posterior approach is most commonly used, through the posterior calyx rather than into          the renal pelvis, as it avoids damage to the posterior branches of the renal artery, which are            closely associated with renal pelvis.
Indications of PCNL:
• Obstructive uropathy (contraindication for ESWL)
• Large volume stone (>2 cm), stag horn calculi
• Other modalities failure (Ureteroscopic failure or ESWL failure)
• Lower pole calyceal stone.
• Difficult (hard) stones for ESWL: Brushite, Hydroxyapatite, Cystine, Calcium oxalate monohydrate (BHC-2)
Complications
• Injury to other viscera like pleura (MC), colon, spleen
• Bleeding, urinary extravasation
• Retained fragments
• Sepsis

Ureteric calculi

Proximal and mid-ureteral Stones:
• Stone ≤ 1 cm: ESWL is primary approach. Ureteroscopy is preferred in failed ESWL, distal               obstruction or impacted stones.
• Stone > 1 cm: Ureteroscopy is primary approach. PCNL for large proximal stones or impacted calculi.
Distal ureteral stones:
• Stone ≤ 1 cm: ESWL and Ureteroscopy equally successful. Ureteroscopy is the primary                  approach.
• Stone > 1 cm: Ureteroscopy
Remember: For all ureteric stones, ureteroscopy is the primary approach except ≤ 1 cm proximal and mid-ureteral stones.

Patient with cystinuria with multiple renal stones should be treated with increase urine volume (high fluid intake), alkalinization of urine, Penicillamine and tiopronin.