The mean Hounsfield unit range acquired from different slices produces superior predictive accuracy for pyonephrosis in obstructive uropathy.

PURPOSE: To determine the non-contrast computer tomography imaging features of pyonephrosis and evaluate the predictive value of Hounsfield units (HUs) in different hydronephrotic region slices. MATERIALS AND METHODS: We retrospectively reviewed data from patients with hydronephrosis who had renal-ureteral calculi. All patients were categorized into pyonephrosis and simple hydronephrosis groups. Baseline characteristics, the mean HU values in the maximal hydronephrotic region (uHU) slice, and the range of uHU in different slices (ΔuHU) were compared between the two groups. Univariate and multivariate analyses were performed to identify risk factors for pyonephrosis. RESULTS: Among the 181 patients enrolled in the current study, 71 patients (39.2%) were diagnosed with pyonephrosis. The mean dilated pelvis surface areas were comparable between patients with pyonephrosis and simple hydronephrosis (822.61 mm² vs. 877.23 mm², p=0.722). Collecting system debris (p=0.022), a higher uHU (p=0.038), and a higher ΔuHU (p<0.001) were identified as independent risk factors for pyonephrosis based on multivariate analysis. The ΔuHU sensitivity and specificity were 88.7% and 86.4%, respectively, at a cutoff value of 6.56 (p<0.001), whereas the sensitivity and specificity for detecting pyonephrosis at a uHU cutoff value of 7.96 was 50.7% and 70.9%, respectively (p=0.003). CONCLUSIONS: Non-contrast computer tomography was shown to accurately distinguish simple hydronephrosis from pyonephrosis in patients with obstructive uropathy. Evaluation of the ΔuHU in different slices may be more reliable than the uHU acquired from a single slice in predicting pyonephrosis.

High attenuation value in non-contrast computer tomography can predict pyonephrosis in patients with upper urinary tract stones.

To evaluate whether the higher attenuation value [Hounsfield unit (HU)] in non-contrast CT can predict pyonephrosis in patients with upper urinary tract stones (UTS). Between October 2019 and October 2021, patients with hydronephrosis or pyonephrosis secondary to upper UTS were retrospectively searched in our study. All patients with UTS were treated with percutaneous nephrostomy, percutaneous nephrolithotomy, retrograde ureteral stent or transurethral ureteroscope lithotripsy. We excluded patients treated with extracorporeal shock-wave lithotripsy. Patients whose CT was not performed in our hospital or treated in another hospital were also excluded. Clinical data regarding basic information, clinical feature, Calculi-related indicators, HU values of the renal pelvis, the thick wall of the renal pelvis on CT were collected. Univariate and multivariate logistic analyses were performed. Receiver operative characteristic curves were drawn to predict pyonephrosis. A total of 240 patients with UTS were retrospected in this research, 191 patients had hydronephrosis (Group 1), and 49 patients had hydronephrosis with pyonephrosis (Group 2). The HU value of the renal collecting system in Group 2 (mean, 15.46; range, +1/+30) was significantly higher than that in Group 1 (mean, 5.5; 5 range -6/+24) (P = .02); the receiver operative characteristic curve analysis revealed that the best cut-off value of 9.5 could predict the presence of pyonephrosis, with 71.4% sensitivity and 70.2% specificity (area under the curve = 0.613; 95% CI: 0.514-0.713). In this study, we found the HU attenuation value of the renal collecting system can be used to distinguish pyonephrosis from hydronephrosis in patients with UTS.

[A Case of Pyonephrosis Due to Urethral Stent Forgotten for 4 Years].

A 53-year-old woman had left pyonephrosis and bladder stone. A double-J ureteral stent was placed for left ureterostenosis and she was lost to followup. Five years later, she had back pain. Computed tomography revealed left hydronephrosis, pyonephrosis and bladder stone. After drainage by percutaneous nephrostomy and antibiotic treatment, left nephroureterectomy was performed. She has been free from recurrence of infection for 3 months after the surgery.

A Nautilus kidney.

We report a 71-year-old woman who presented with unilateral flank pain and sepsis. A computed tomographic (CT) scan demonstrated left-sided hydronephrosis. Subsequent percutaneous nephrotomy drainage showed pus-like material, confirming the diagnosis of pyonephrosis. The ureteral stricture was caused by previous radiation injury for cervical cancer in this ESRD patient who was on chronic dialysis for years. In our case, the grade IVB hydronephrosis is a result of an extremely atrophic kidney, pyonephrosis, and ureteral stricture. The CT section of pyonephrosis in an extremely atrophic kidney resembles a sagittal section of a Nautilus shell, as the shell corresponds to the diffusely thinned renal cortex.

A novel use of attenuation value (Hounsfield unit) in non-contrast CT: diagnosis of pyonephrosis in obstructed systems.

PURPOSE: To evaluate the predictive value of attenuation value (HU) in renal pelvis urine for detecting renal pelvis urine culture (RPUC) positivity in obstructed urinary systems. METHODS: The study group consisted of patients who had nephrostomy insertion performed because of obstructed system and suspicion of pyonephrosis and percutaneous nephrolithotomy (PCNL) patients who had obstructed calculi. Group 1 consisted of RPUC positive 28 patients during nephrostomy insertion or needle access in PCNL and group 2 consisted of 23 patients with negative RPUC. RPUC results and non-contrast computed tomography measurements [Hounsfield unit (HU)] were compared between group 1 and group 2. A cut-off value was determined for HU. All patients were grouped according to whether they were above or below this value. RESULTS: The median HU calculated from the renal pelvis was - 8.5 (range - 29/- 1) and 10 (range- 4/+ 17) (p < 0.001) in group 1 and group 2, respectively. The cut-off value of HU that predicted positive RPUC was 0. Sensitivity and specificity of HU when considering this cut-off value were 100% and 96%, respectively (p < 0.001). Whereas RPUC positivity was found in 96.6% (28/29) of patients with HU < 0, there were no patients with HU > 0 where RPUC positivity was detected (p < 0.001). CONCLUSION: In this cohort, we found that HU of the urine in the renal pelvis can be used to predict RPUC positivity.

Urinary tract infection due to anaerobic bacteria in a two-month-old infant.

The significance of anaerobic bacteria as a pathogen in urinary tract infection (UTI) in children is unclear. A two-month-old infant presenting with poor feeding received a diagnosis of polymicrobial anaerobic UTI by next-generation sequencing and was found to have obstructive uropathy. Anaerobic bacteria may be a cause of UTI in children with urinary tract obstruction.

Pyonephrosis as the first symptom of congenital hydronephrosis in a 6-year old girl.

Pyonephrosis in the course of hydronephrosis usually provides to total or near-total loss of renal function. In adults pyonephrosis usually results from urolithiasis. In children usually congenital urinary tract anomalies are present as contributing factors. CASE REPORT: 6-year old girl was admitted to the hospital because of 2-day history of high fever, abdominal pain, progressive deterioration of general condition and ultrasonographically (US) detected left hydronephrosis. US on admission showed grossly dilated left renal collecting system together with extensive echogenic debris and laboratory tests highly elevated inflammatory markers. Once diagnosis of pyonephrosis was established on the basis of clinical picture and US as well as laboratory tests results, nephrostomy tube was placed percutaneously. Pus culture obtained during placement of nephrostomy showed E.Coli ESBL (-) growth. Intensive antibiotic treatment (Meropenem) was continued for 3 weeks, nephrostomy was removed after 12 days after receiving normal urine. Further evaluation of urinary tract (US and computed tomography urography) showed large hydronephrosis due to ureteropelvic junction obstruction, while dynamic scintigraphy obstructive renogram with grossly diminished left kidney function to 20% of differential renal function. The girl was referred for operative treatment on urgent basis. Intraoperatively long distance utreteropelvic junction stenosis was found and dismembered Anderson- Hynes pyeloplasty was performed. During 2-years follow-up postoperatively US showed gradually decrease of dilatation of left renal collecting system, while dynamic scintigraphy revealed permanent improvement of drainage together with almost normal renal function (up to 45%). No urinary tract infections were noted. CONCLUSIONS: Proper management of pyonephrosis in hydronephrotic kidney due to congenital ureteropelvic junction obstruction enables good final result of treatment.

Computerized tomography attenuation values can be used to differentiate hydronephrosis from pyonephrosis.

PURPOSE: To determine the diagnostic value of computerized tomography (CT) in differentiating pyonephrosis from hydronephrosis on the basis of attenuation values (Hounsfield unit-HU). METHODS: Data of the patients with grades 1-3 hydronephrosis on abdominopelvic CT, who underwent nephrostomy tube placement for decompression of the collecting system, were retrospectively analyzed. Patient demographics and CT findings were recorded along with the first access urine culture results. Three physicians calculated the surface areas and the attenuation values of the dilated collecting systems using the system software. Mean HU of pyonephrosis and hydronephrosis cases was compared. RESULTS: A total of 105 patients with the mean age of 47.7 ± 15.5 (range 20-80) were included. The interclass correlation coefficient of three physicians was 0.981 for HU measurement and 0.999 for calculation of collecting system surface area. Of the patients, 47 (44.8 %) had pyonephrosis. Mean surface areas of the collecting system were similar in patients with pyonephrosis and hydronephrosis (1481.13 ± 1562.94 vs. 1612.94 ± 2261.4 mm2, p = 0.735). Urine cultures were positive in all patients with pyonephrosis, whereas 12.7 % of hydronephrosis cases had bacterial in first access urine culture. The HU of the patients with pyonephrosis was significantly higher that that of patients with hydronephrosis (13.51 ± 13.29 vs. 4.67 ± 5.37, p = 0.0001). Having a HU of 9.21 or over diagnosed pyonephrosis accurately with 65.96 % sensitivity and 87.93 % specificity. CONCLUSION: Measuring attenuation values of the collecting system may be useful to differentiate pyonephrosis from hydronephrosis. Diagnosing pyonephrosis accurately may avoid septic complications.

Infectious and inflammatory diseases of the kidney.

Although the most common renal infection, acute pyelonephritis, can typically be diagnosed on clinical and laboratory examinations, radiologic studies play a role in evaluating for complications and in examining the high-risk patient for more serious complications and atypical infections. It is imperative that the radiologist be familiar with renal infections beyond the common acute pyelonephritis.

Ultrasonographic features of pyonephrosis in dogs.

Pyonephrosis refers an infected hydronephrotic kidney which arise from pyelonephritis followed by exudate accumulation in a dilated renal pelvis or hydronephrosis followed by ascending infection. Pyonephrosis may cause serious systemic complications, making prompt and reliable diagnosis critical. Clinical and ultrasonographic findings are used for the diagnosis of pyonephrosis in humans, but these findings have not been investigated in dogs. We reviewed ultrasonographic features in pyonephrosis in 18 dogs. Ten dogs with hydronephrosis were also evaluated to compare with the pyonephrosis patients. In most dogs with pyonephrosis, hyperechoic contents completely filled the dilated renal pelvis (n = 8) or a fluid-debris level was observed (n = 8). Hyperechoic contents were dispersed in renal pelvis in only two of the 18 dogs. Hyperechoic, edematous mesentery, and peritoneal and retroperitoneal effusion, which represented peritoneal and retroperitoneal inflammation, were observed in the perinephric region in 11 dogs. Compared with pyonephrosis, and as expected, hydronephrosis was characterized by anechoic contents within the urine-filled collecting system and there were no definitive findings to suspect peritonitis. Thus, there is a distinct difference in the sonographic appearance of pyonephrosis vs. hydronephrosis in dogs.

State of the art: imaging of renal infections.

Infections of the urinary tract are common and account for a large number of patient encounters in the ambulatory and emergency department setting. Their severity and presentation varies, and although uncomplicated infections can often be diagnosed and treated based on clinical and laboratory findings alone, diagnostic imaging may be necessary in some cases to guide appropriate medical or surgical therapy. We will briefly describe the indications for imaging known or suspected upper urinary tract infections, and the relative benefits and limitations of the different imaging modalities for a given clinical presentation. This will be followed by a discussion of various types of renal infections with a pictorial review of their imaging appearances and differential diagnoses.