Prognostic factors in retroperitoneal fibrosis

Abstract

The aim of this study is to evaluate effective prognostic factors in the evolution of patients with retroperitoneal fibrosis and to establish the validity of fractal analysis in determining the disease severity in these patients.

Material and methods: This study included 19 patients (M/F: 5/14) treated for idiopathic retroperitoneal fibrosis and bilateral obstructive renal failure between Jan 2004-Dec 2008. Patients were identified retrospectively, searching for patients diagnosed with IRF, after retroperitoneal biopsy or, in most cases the diagnosis rested on radiological findings, especially CT, with identification of a retroperitoneal mass, the absence of other demonstrable renal or ureteric disease or any other pathology that could explain the findings. CT was very useful in describing the retroperitoneal mass around the aorta and inferior vena cava, the extent of the lesion and for monitoring the response to surgical treatment during the follow-up. The data were evaluated about medical history, physical examination findings, laboratory tests (serum urea and creatinine, blood sugar, sodium, potassium, bicarbonate levels, serum pH, uric acid, haematocrit, white blood cell count), imaging methods (renal ultrasound, abdominal CT-scan, MRI). At admission all patients had active disease with obstructive renal failure and underwent bilateral ureteric stenting in order to normalize the BUN levels. After normalizing of BUN levels, ureterolysis and omental wrapping was performed. Postoperatively, ureteric stents were removed after 1 month and remission of renal disfunction was obtained in approximately 5 months (range 2-10 months). All patients were followed for at least 1 year. Patients were regularly checked every 3 months.

Results: Of the 19 patients, there were 5 men and 14 women. The median age at diagnosis of RF was 50 years (range 42-64 years). The most frequent presenting symptoms were back or abdominal pain, weakness, weight loss, oligoanuria, arterial hypertension and mild fever. The duration of symptoms before diagnosis ranged from 6 to 18 months. At presentation all patients had active disease, presenting renal dysfunction with a median serum creatinine of 5.18 mg/dl (range 1-15.4 mg/dl). Most of the patients had moderate bilateral hydronephrosis (2nd degree hydronephrosis). In our study, all patients had excellent prognosis, with full recovery of renal function in 78% of cases (15 patients). The fractal dimension of the fibrosis mass contour correlates with level of renal function impairment. Even more, the fractal dimension seems to slightly variate between CT evaluations (1.30 +/- 0.1), suggesting a non aggressive pattern of extension of the fibrotic mass characteristic for benign lesions.

Conclusions: The imaging parameters did not predict the disease severity, except the increase in fractal dimension of fibrosis surface area. Efficacy of bilateral ureteric stenting in improving renal function is limited in most of the cases. Dispite the level of renal function impairment at admission, full recovery can be achieved after bilateral ureteric stenting/nephrostomy and ureterolisis.

Fig 1

Multiplanar frontal reconstruction in native CT scan after bilateral ureteric stenting (transureteric section)

Fig1

Hausdorff coverage dimension

Fig2

Better approximation of Hausdorff

Fig3

Better approximation of Hausdorff with limit coverages

Fig 1.1

The initial image

Fig 1.2.a

Extracted contour classical method

Fig 1.2.b

Extracted contour proposed method

Fig 3

Creatinine vs. Fractal dimension

Fig 4

Serum creatinine levels vs. hydronephrosis degree at admission.

Fig 5

Serum creatinine levels vs. fibrosis width at admission

Fig 6

Postoperatory CT scans at 3 and 6 months. In figure A, low–attenuation halo is observed around the right ureter. Figure B, full remission of fibrotic mass at 6 months after surgery