A simple processing method allowing comparison of renal enhancing volumes derived from standard portal venous phase contrast-enhanced multidetector CT images to derive a CT estimate of differential renal function with equivalent results to nuclear medicine quantification.

As iodinated contrast medium is cleared by glomerular filtration, it should be possible to apply the same principles utilized in radionuclide studies to derive differential renal function by comparison of enhancing renal volumes derived from contrast enhanced multidetector CT (CEMDCT). Having established a technique iteratively which appeared successful, a retrospective study was performed using 25 consecutive patients with a wide range of urological conditions who had undergone both CEMDCT, including the renal area in the portal venous phase, and nuclear medicine (NM) assessment of renal function with no urological intervention between the studies. Proprietary volume software was used to quantify the volume and attenuation of each kidney, the products of which (after subtraction of soft tissue attenuation derived from a region of interest over psoas) gave right and left enhancing renal volumes. The contribution by each kidney as a percentage of total renal enhancing tissue was derived. Comparison with NM studies resulted in excellent correlation of relative renal function by CEMDCT and NM assessments having a regression of near unity and a Pearson's correlation coefficient of 0.96. Bland Altman and Passing Bablock tests confirmed good agreement between the two methods with no bias. This is a simple, practicable processing technique using standard portal venous phase CEMDCT images to quantify differential function. This technique may allow a one-stop CT assessment of both anatomy and function.

Descending urethral ultrasound of the native and reconstructed urethra in patients with hypospadias.

A retrospective study, over a 7 year period, examining the use of descending urethral ultrasound in corrected and uncorrected hypospadias was performed. 15 examinations were performed on 14 patients; 12 patients had undergone previous surgery for hypospadias, ranging from urethral reconstruction to stricture dilatation. Eight strictures, four irregular urethras, two normal post-operative urethras and one urethral valve were demonstrated. All the clinically significant abnormalities (those which impaired the flow of urine) demonstrated by ultrasound were confirmed with subsequent urethroscopy or contrast urethrography. This small series illustrates the application of descending urethral ultrasound in patients with hypospadias who are difficult to examine with more conventional radiographic techniques.

Is the conservative management of ureteric calculi of > 4 mm safe?

OBJECTIVE: To determine the safety of the conservative management of ureteric calculi of > 4 mm in diameter, using mercapto-acetyltriglycine (MAG3) radioisotope renography to monitor renal parenchymal function. PATIENTS AND METHODS: Patients with symptomatic unilateral ureteric calculi were recruited prospectively. After confirming the position of the stone using contrast urography, a MAG3 radioisotope renogram was taken within 48 h of admission and again 1 month after the patients became stone-free. The indications for intervention were ipsilateral loss of function (>/= 5% loss), infection, pain or any combination of these factors. The recovery of function was determined by follow-up renography. RESULTS: In all, 54 patients were recruited; 18 were initially allocated to conservative treatment although four later required intervention for pain. The remainder required early intervention for pain (eight), diminished function only (15) or diminished function with infection (13). Of the 54 patients, 28% had 'silent' loss of renal function at presentation. No calculi of > 7 mm diameter passed without intervention. The mode of initial management was determined according to individual clinical need. The upper tracts of all patients were relieved of obstruction and all patients were rendered stone-free. Intervention for reduced function only (at

An unusual case of renal cell carcinoma with two rare metastases.

It is well known that renal cell carcinoma metastasizes to unusual sites. We report a case in which two rare sites of metastasis, the maxilla and contralateral ureter, appeared in a single patient.

A review of antegrade stenting in the management of the obstructed kidney.

OBJECTIVE: To review experience in the management of the obstructed ureter using antegrade stenting in a variety of conditions. PATIENTS AND METHODS: Between 1984 and 1993, 41 patients (mean age 57 years, range 9-83) had antegrade stents placed by an experienced interventional radiologist. The causes of obstruction were urological in 27, gynaecological in eight, colorectal in three and miscellaneous in three. RESULTS: The overall success rate for antegrade stent insertion was 83% and the failure rate was greatest (four of six) in cases of ureteric injury following gynaecological procedures. There were no immediate complications. CONCLUSION: Antegrade stenting can be used as a temporary or permanent solution to ureteric obstruction. The technique is safe, acceptable to patients and avoids the need for a general anaesthetic.

Data collection and complication rates in clinical audit.

Audit data were collected continuously between February 1988 and July 1991. For the initial period (February 1988-June 1990) data were collected by monitoring of ward admission and discharge records and by collecting data from operating theatre records whilst complications were noted in a 'complications book' which was kept on the notes trolley. In July 1991, when a computerized system for storing and processing audit data was introduced into the department, the methods of data collection changed. For each patient a proforma was attached to the clinical notes which was filled in at each stage of the hospital stay. On this proforma was a list of possible complications which were ticked, as appropriate, at the time of discharge from hospital. We have reviewed the results of clinical audit during these two periods. The number of operations performed per month fell slightly in the latter period (p = 0.005). However, there was a significant increase in both the number of complications (p < 0.0001) and in the complication rate (p < 0.0001). Further analysis showed that there was a similar increase in the number of recorded major and minor complications, and that this increase was also seen even when changes in medical personnel were accounted for. We suggest that the increased complication rate recorded in the latter period reflects the change in the method of data collection. This has important implications when comparing outcome measures for clinical departments.

Rectal obstruction secondary to carcinoma of the prostate treated by transanal resection of the prostate.

Rectal obstruction caused by carcinoma of the prostate is uncommon. If the disease does not respond to either hormonal treatment or radiotherapy, the only surgical means of relieving the obstruction has been the formation of a colostomy. We present an alternative treatment, since many of these patients are elderly with a short life expectancy and they may have difficulty coping with a stoma. Seven transanal endoscopic resections of the prostate (TARP) have been performed on 5 patients. The procedure is not without complications, but it does offer simple surgical palliation of the rectal obstruction and obviates the need for a colostomy.

Identifiable factors in post-prostatectomy haemorrhage: the role of aspirin.

Post-operative haemorrhagic complications following the ingestion of aspirin have been reported after several types of surgery, most notably coronary artery bypass surgery. In this study, aspirin ingestion also appeared to be a significant aetiological factor in post-prostatectomy haemorrhage. This is explained in terms of its inhibitory effect on platelet aggregation. A history of aspirin ingestion should be carefully sought and its haemorrhagic implications considered prior to prostatectomy.

Delayed recognition of an intersphincteric abscess as the underlying cause of Fournier's scrotal gangrene.

It has recently become increasingly clear that Fournier's gangrene, far from being 'idiopathic' as initially thought, often originates from preexisting perianal or periurethral sepsis. The aetiology is discussed and an example quoted where the associated intersphincteric abscess was not recognised until some 3 months after the initial presentation. It is recommended that all patients presenting with Fournier's gangrene be examined by an experienced rectal surgeon early in the course of their illness.

Upper urinary tract compliance: its importance in obstructive hydronephrosis.

Improvements in diagnostic modalities over the last 15 years have meant that obstruction can now be diagnosed accurately in dilated upper tracts. However, it is no longer sufficient to diagnose obstruction in a hydronephrotic kidney; it is necessary to determine the likelihood of functional deterioration in that kidney by measuring its elastic distensibility (compliance). 111 pressure flow studies have been reviewed in an attempt to measure the compliance of each upper tract under study and to assess its clinical implications. Good compliance was seen in 64 dynamically unobstructed renal units as well as in 16 obstructed systems. These 16 obstructed systems with good compliance had less significant degrees of obstruction than a group of 31 obstructed systems with poor compliance. Obstruction with good compliance was associated with preservation of renal function as measured by diuresis renography whilst impaired function was seen in systems with obstruction and poor compliance. Systems with good compliance and obstruction may not necessarily need surgery to relieve obstruction but instead could be managed by avoiding a high fluid intake which is liable to produce a pressure rise in the kidney. Poor compliance or functional deterioration are indications for immediate relief of the obstruction.

Does good upper tract compliance preserve renal function.

We reviewed 111 pressure flow studies in an attempt to measure the compliance of each upper tract under study and to assess its clinical implications. Good compliance was seen in 64 dynamically unobstructed renal units as well as in 16 obstructed systems. The latter systems had less significant degrees of obstruction than a group of 31 obstructed systems with poor compliance. Obstruction with good compliance was associated with preservation of renal function as measured by diuresis renography, while impaired function was seen in systems with obstruction and poor compliance. The clinical implications of correlating the degree of obstruction, compliance and renal function are discussed.

"The distal nephron index": a measure of obstructive nephropathy in experimental hydronephrosis.

An experimental model is described in rabbits where chronic partial ureteric occlusion and permanent renal pelvic cannulation were performed. For periods of up to three months, parameters of distal nephron function were measured repeatedly and pressure-flow studies performed. Fractional water clearance, free water clearance/GFR ratio and the relative intrapelvic pressure (IPP) on perfusion were increased (P less than 0.01) as a result of partial ureteric occlusion. A new parameter, "the distal nephron index", is described which is also raised in obstruction (P less than 0.01) and which exhibits a linear correlation with relative IPP (r = +0.40; P less than 0.05) not demonstrated by the other distal nephron function measurements. The implications of this relationship in the assessment of upper tract dilatation are discussed.

The biomechanical principles of upper urinary tract pressure-flow studies.

An experimental model is described in which the relationship between relative renal intrapelvic pressure and perfusion rate at varying degrees of ureteric obstruction was investigated in the rabbit ureter. There was smooth, laminar (Poiseuille) flow in the ureter over a wide range of flow rates even in the presence of sharp constrictions. The theoretical basis of these findings in terms of the fluid mechanics of collapsible tubes is defined and their importance in the assessment of equivocal upper tract obstruction discussed.