Lawrence R. Bigongiari

An Algorithm for Volume Estimation Based on Polyhedral Approxi mation

A volume algorithm is established which uses the data generated by computed tomography (CT) or ultrasound scans. The algorithm is based on a polyhedral reconstruction of an object of interest. Phantom studies indicate that the algorithm calculated volume is accurate within 3 percent. In a controlled clinical experiment on a laboratory animal, the algorithm calculated volume showed a maximum error of about 5 percent. In less controllable applications to human clinical data, volume calculations showed variations ranging up to 16 percent.

The seldinger approach to percutaneous nephrostomy and ureteral stent placement

The Seldinger approach to percutaneous nephrostomy and ureteral stent placement involves needle-puncture, guide wire introduction, tract dilation and catheter placement as in angiography. We have used this approach on 101 obstructed renal units without significant complication.Techniques are described in detail with special attention given to those for negotiating tortuous ureters. A guide wire through the kidney to the bladder can be used to place an indwelling stent either from above or below in order to free the patient completely from external appliances.These techniques afford exciting new alternatives in the management of common urological problems. Most of all, they offer nonoperative palliation to terminal cancer patients and suitable alternatives to patients too ill to undergo surgery.

Conversion of percutaneous ureteral stent to indwelling pigtail stent over guidewire.

A ureteral stent placed percutaneously through a nephrostomy can be readily exchanged endoscopically for a ureteral indwelling pigtail stent over a percutaneous guide wire. Percutaneous antegrade stent placement can sometimes be accomplished when retrograde placement cannot. We report 10 successful conversions to indwelling stent in 11 cases. In 1 case the percutaneous guide wire could not be retrieved endoscopically because of a bleeding tumor in the bladder. No serious difficulties or complications were encountered. The percutaneous approach offers an alternative method of providing internal urinary diversion if retrograde ureteral indwelling stent placement has failed.

Vagal pseudohemorrhage after percutaneous biopsy.

Vagal reaction occurring after percutaneous needle biopsy can mimic hypovolemic shock. Misdiagnosis has led to unnecessary surgery and death. Both vagal reaction and hypovolemia can produce hypotension, pallor, and diaphoresis. Vagal reaction is characterized by bradycardia or absence of tachycardia. On the other hand, hypovolemia is characterized by tachycardia. Atropine in large doses is the treatment of choice for vagal reaction, when treatment is necessary. Radiologists involved in percutaneous biopsy procedures should be aware of vagal reactions and should known how to treat them.

Subcutaneous implantation of percutaneous ureteral stents

The authors describe their experience with subcutaneous implantation of percutaneous ureteral stents. Three of the five procedures were complicated by infection, urine leak and/or chronic drainage at some time during their course. One patient developed pressure changes of the skin overlying the implanted tube. The problems encountered in this initial experience are avoidable. Subcutaneous implantation of percutaneous ureteral stents can be useful in the management of appropriate patients.

Renal pseudoenlargement due to masses in posterior pararenal space

Two patients presenting with acute flank pain had unilateral smooth enlargement of a kidney on excretory urography with associated attenuation of the collecting system. This presentation suggested intrinsic renal disease, but sonography showed the urographic findings to be due in each case to a mass in the posterior pararenal space. By displacing the kidney anteriorly and away from the x-ray film, such masses will result in radiographic enlargement of the renal outline, i.e., renal pseudoenlargement. The distinction between true renal enlargement and pseudoenlargement may be made by sonography.

Pseudohydronephrosis on bone scan due to crossed renal ectopia.

We present a patient with crossed renal ectopia whose bone scan gave the appearance of unilateral hydronephrosis with contralateral absent or nonfunctioning kidney. An excretory urogram revealed crossed renal ectopia without obstruction. The axiom that unilateral absence of a kidney without previous nephrectomy should stimulate a search for ectopic kidney applies equally well to the bone scan as to the excretory urogram.

Vagal hypotension after percutaneous biopsy: Possible confusion with hypovolemic shock

Vagal hypotension can occur after percutaneous biopsy and be misdiagnosed as hypovolemia due to hemorrhage. Inappropriate exploratory surgery and death have resulted. Increased vagal tone or massive discharge is characterized by hypotension with bradycardia or lack of tachycardia and can occur after many stimuli including contrast medium injection, anxiety, and needle insertion. Vagal reactions can be mild and self-limited, but can also progress to cardiac arrest. Atropine 0.6 to 0.8 mg intramuscularly or intravenously in increments up to 3 mg has been recommended for prompt treatment. Volume expansion is adjunctive.

Parenchymal Diseases of the Kidneys

Radiologic evaluation does not currently play a primary role in the definitive diagnosis of diseases of the kidney. Specific diagnosis is based upon clinical pattern, laboratory findings, and renal biopsy. Imaging techniques are ancillary procedures used to detect anatomy, assess function, and evaluate for complications or associated abnormalities. The combination of excellent anatomic delineation and information regarding functional status provided by urography, retrograde pyelography, nuclear medical examinations, ultrasound, computed tomography, magnetic resonance imaging, and angiography does not provide results distinctive enough to allow definitive diagnosis. There is significant overlap of findings on any given examination so that even the most specific pattern, i.e., the microaneurysms seen on renal angiograms in polyarteritis nodosa, is also seen in several other entities, such as systemic lupus erythematosus (SLE) and intravenous drug abuse (Longstretch et al. 1974; Halpern 1971; Lignelli and Buchheti 1971).