Percutaneous Endourology Workup

Updated: Dec 11, 2018
  • Author: Michael Grasso, III, MD; Chief Editor: Bradley Fields Schwartz, DO, FACS  more...
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Laboratory Studies

Preoperative considerations

A thorough history should be obtained and a physical examination should be performed prior to any percutaneous renal procedure.

Special attention should be paid to the following historical factors: anticoagulation, bleeding disorders, contrast-medium reactions, malignancy, obesity, spinal cord injury, and history of urinary tract infections with the urine cultures and sensitivities.

Coagulation profile

This includes prothrombin time, with international normalized ratio (INR), activated partial thromboplastin time, and platelet count.

The only contraindication to percutaneous renal access is an uncorrected coagulopathy. Correcting any abnormalities prior to percutaneous access is essential. Thrombocytopenia should be corrected with platelet administration. Aspirin and clopidogrel (Plavix) should be stopped preoperatively to allow for platelet function to be optimized.

For elective procedures, patients on Coumadin should have their coagulation factors normalized prior to surgery.

Overall renal function

This should be evaluated prior to performing percutaneous surgery. Typically, a blood urea nitrogen and creatinine suffice.

Complete blood cell count

A complete blood cell count is essential prior to performing percutaneous access.

Intraoperative and postoperative bleeding is a possible complication of percutaneous renal surgery, and knowledge of the patient's baseline hematocrit is critical in patient management if significant bleeding occurs.

In addition, the white blood cell count may indicate a concurrent infectious process requiring more aggressive antibiotic prophylaxis.

Urinalysis and urine culture

Prior to manipulation of the urinary tract, ruling out urinary tract infection is essential. Percutaneous manipulation of the kidney may rapidly lead to sepsis in the setting of infection and/or obstruction.

Appropriate antibiotic coverage is useful prior to the procedure and should be available during the procedure to help prevent intraoperative sepsis.

Patients with known infectious stone burdens may require staged therapy with percutaneous tract maturation, especially if resistant organisms are encountered on preoperative urine cultures.


Imaging Studies

Before placing a percutaneous nephrostomy, baseline diagnostic renal imaging is required. Intravenous or retrograde pyelography and renal ultrasonography are the most common imaging modalities used to define renal anatomy and pathology. Computed tomography, nuclear renography, and magnetic resonance imaging may all be used to define unexpected abnormalities. CT scanning may help reveal any posteriorly lying loops of colon that may overlie a potential nephrostomy tract and may help in planning a safe angle for nephrostomy tube placement. All radiographic studies should be carefully reviewed prior to placement of a nephrostomy tube. In patients with renal ectopy, malrotation, or a history of surgery that would change the perirenal anatomy, CT scanning is particularly useful in planning a safe percutaneous tract into the renal collecting system.

Both ultrasonography and fluoroscopy are useful when nephrostomy placement is planned and performed. Baseline ultrasonography provides useful information prior to the procedure, such as depth and lay of the kidney, location of stone burden, and the degree of hydronephrosis. Every percutaneous renal access procedure is performed with real-time imaging. Fluoroscopy is preferred when precise renal access is required, as with planned intrarenal endoscopic intervention.

Contrast medium–enhanced imaging is essential in defining the intrarenal collecting system. Intravenous pyelography may help define the caliceal system and stone burden if the kidney functions well and is not obstructed. If the renal function is suboptimal, retrograde ureteropyelography can help define the collecting system. Antegrade studies may be performed after initial access is obtained.

A 3-dimensional CT scan with reconstruction images can be used selectively in complicated cases, such as in planning a percutaneous approach to a staghorn calculus in a malrotated kidney or in revealing crossing vessels in a patient with UPJ obstruction. CT urography has recently been used to provide a very accurate anatomical roadmap.

Endoluminal ultrasonography may be used to diagnose and to evaluate the depth of penetration of ureteral and renal pelvic neoplasms, to locate crossing vessels and septa for guiding endopyelotomy of UPJ obstruction, and to identify submucosal calculi. Endoluminal ultrasonography is performed using small (6-10F) high-frequency transducers, which are inserted into a hollow viscus (ie, ureter).


Other Tests

Simple percutaneous renal access procedures are performed with the patient in the prone position while under a combination of local anesthetic and intravenous sedation. Patients who are morbidly obese and those with significant cardiopulmonary disease may not be able to sustain this position. A general anesthetic with endotracheal intubation may be preferable, especially in longer cases, to help avoid inadvertent aspiration. Appropriate medical consultation may be useful in these higher-risk patients.