Role of MRI in the evaluation of acute pyelonephritis in a high-risk population with renal dysfunction: a prospective study.

AIMS: This study aims to evaluate the (a) accuracy of conventional and diffusion-weighted-imaging (DWI) sequences in the diagnosis of acute pyelonephritis and (b) minimum apparent diffusion coefficient (ADC) values for the diagnosis of acute pyelonephritis and the differentiation of renal abscesses from acute pyelonephritis. MATERIALS AND METHODS: Ultrasound, conventional MRI sequences, and DWI were used to evaluate the kidneys in 68 patients suspected to have acute pyelonephritis. Multiple similar regions of interest (ROIs) were placed over the renal parenchyma with visually identifiable diffusion restriction, over the non-diffusion-restricted renal parenchyma of affected kidneys and over the normal kidneys. Corresponding minimum ADCs were noted for analysis. Pyelonephritis was confirmed based on clinical criteria, laboratory findings, and by resolution/development of known complications of pyelonephritis. RESULT: DWI showed the highest sensitivity(100%), while DWI read with T2-weighted imaging (both being positive) showed the highest specificity(100%) for the diagnosis of acute pyelonephritis in our population with a high baseline creatinine. The minimum-ADC of the nephritic diffusion-restricted area in patients with confirmed pyelonephritis was significantly lower than the minimum-ADC in patients without pyelonephritis [(0.934 ± 0.220, mean ± SD) vs (1.804 ± 0.404) × 10-3 s/mm2] (p < 0.001). ROC cut-off of minimum-ADC for the diagnosis of acute pyelonephritis was 1.202 × 10-3 s/mm2 (area under curve 0.978). The minimum-ADC of the abscesses were significantly lower when compared to the minimum-ADC of the nephritic diffusion-restricted portion of the same kidney [(0.633 ± 0.248) vs (0.850 ± 0.191) × 10-3 s/mm2] (p < 0.001). CONCLUSION: DWI is an excellent stand-alone imaging tool that can be combined with conventional sequences for the diagnosis of APN even in patients with high serum-creatinine or other contraindications to intravenous contrast. Further, ADC values can be used to differentiate between renal abscesses and uncomplicated pyelonephritis.

MR urogram findings and diffusion restriction in the renal papilla and calyx in papillary necrosis-a new finding: preliminary report.

Renal papillary necrosis is a clinicopathological entity where any or all of the papillae undergo selective necrosis, which can be demonstrated either radiologically or histologically. The most important causes are diabetes, pyelonephritis, obstructive uropathy, tuberculosis, analgesic abuse or overuse, sickle cell disease and renal vein thrombosis. Although this condition was first described in the 19th century the clinical diagnosis of this condition remains a problem to this day. Uncomplicated papillary necrosis may initially remain occult to imaging by ultrasound and non-contrast CT, but may later be complicated by obstructive uropathy. A few studies have described renal papillary necrosis on CT urogram. In this case series, the authors describe the finding of calyceal filling defect with diffusion restriction in the calyx and the tip of the renal pyramid on MR urogram, along with other findings that are classically seen on intravenous urogram or CT urogram. To the best of our knowledge, the finding of diffusion restriction at the tip of the renal pyramid has not been described before. Further, literature review showed only a single study describing the classical findings of papillary necrosis on an MR urogram. The early diagnosis of papillary necrosis on MR imaging equips the radiologist to suggest short-term clinical and radiological follow-up to check for the development of hydronephrosis. Additionally, such risk stratification may enable early ureteric stenting to prevent the development of obstructive uropathy.

A case report of racemose pattern of intracranial tuberculoma with brain stem and hypophyseal involvement developing paradoxically during treatment.

Tuberculosis involving the central nervous system, a source of considerable morbidity and mortality, forms 5-10% of the disease burden associated with tuberculosis. Central nervous system tuberculosis may present as meningitis, tuberculoma, abscesses, cerebritis or miliary tuberculosis. The most common site of tuberculoma has been reported to be at the grey-white matter junction and the periventricular region. They may even be found in the epidural, subdural and subarachnoid spaces, and the brain stem, with the rarer sites of involvement being the cavernous sinus, sella turcica, hypophysis, hypothalamus, sphenoid sinus and the mastoid air cells. Although tuberculosis is very common in developing countries, with the increasing prevalence of immunosuppression owing to human immunodeficiency virus and patients surviving chemotherapy or organ transplantation, the incidence of tubercular infections has been rising in developed countries. The authors report a case of intracranial tuberculosis in a human immunodeficiency virus-negative patient, who underwent incomplete treatment for tubercular peritonitis and presented with unilateral ptosis. Tuberculous involvement was noted in a racemose pattern in the subarachnoid space, cavernous sinuses, suprasellar cistern and parasellar region. To the best of our knowledge, the term racemose pattern of tuberculoma has not been described before, while about 10 cases of tuberculoma involving the cavernous sinuses have been reported in the literature. Furthermore, the racemose pattern of tuberculosis in the subarachnoid space, as well as involvement of the cavernous sinus, hypothalamus, pituitary and the cisterns, developed paradoxically after initiation of antitubercular chemotherapy.