A pregnant 31-year-old woman at 22 weeks’ gestation presented with a 48-h history of right renal angle pain, nausea, decreased appetite and diarrhoea. The patient was afebrile. The blood pressure was 90/59 and pulse was 87 beats per minute. Foetal movements were normal. Laboratory values included a neutrophilia of 9 × 109/l, a serum C-reactive protein of 66 mg/l and creatinine of 66 μmol/l. Urinary microscopy demonstrated white cells of > 1000/μl with positive urinary cultures for Escherichia coli. The patient consented to the clinically indicated imaging tests and procedures performed including a detailed discussion of the associated foetal risks with each intervention and consent to the use of anonymised images for research purposes.
Ultrasound was performed using a curvilinear 3–5-MHz abdominal ultrasound probe (Toshiba, Tokyo, Japan). This demonstrated moderate right hydronephrosis and a percutaneous nephrostomy was inserted under ultrasound guidance to treat suspected urosepsis confirmed by the clinical observation of pyuria in the drainage bag after nephrostomy placement.
A day later, MR imaging of the abdomen was performed to determine the level and cause of obstruction. The examination confirmed decompression of the right renal collecting system but the level and cause of obstruction could not be determined due to non-distension of the right renal pelvis and ureter. The patient’s symptoms had resolved.
Seven days after nephrostomy placement, the referring urologic surgeon considered the removal of the nephrostomy after a successful clamping trial of 24 h but wished to determine if the obstruction was due to renal calculi or physiological compression by the gravid uterus. In the light of the unrevealing MR imaging, antegrade pyelography appeared to be indicated. However, a solution that minimised the patient and foetal exposure to ionising radiation was sought.
Gd-enhanced urography was considered, but following a literature search, which confirmed that the potential effects of Gd-chelate adminisitration on the foetus had not been determined yet, and one animal study suggesting teratogenicity [9], the decision was taken to perform antegrade MR pyelography using sterile water and T2-weighted imaging.
The patient was placed supine in a 1.5-T Magnetom Symphony scanner (Siemens, Erlangen, Germany). A T2-weighted half Fourier acquisition single-shot turbo spin-echo (HASTE) coronal sequence was performed as a control prior to injection with a standard body coil (excitation time 66 ms, echo train length 128, flip angle 180°, number of excitations 1, matrix 240 × 256, slice thickness 4 mm, TA (acquisition time) 13 s). The right nephrostomy catheter hub was sterilised using chlorhexidine and 60 mL of sterile water were slowly injected. Serial coronal and axial HASTE sequences were performed and reviewed immediately by the radiologist to confirm adequacy. Antegrade MR pyelography confirmed gradual tapering of the right lower ureter just above the level of the gravid uterus (Fig. 1). No calculus was demonstrated at this level. Non-dependent filling defects in the right renal pelvis and upper ureter were confirmed to be transient on serial scanning, consistent with small air bubbles due to hand injection (Fig. 2). Antegrade MR pyelography confirmed the cause of urosepsis to be a physiologic obstruction due to the gravid uterus. The nephrostomy was clamped again for a further 24 h; the patient remained asymptomatic thus clinically excluding ongoing obstruction. The nephrostomy was therefore removed and the patient remained well at 12-month clinical follow-up.
