Unilateral and bilateral acute pyelonephritis: differences in clinical presentation, progress and outcome

Usefulness of computed tomography in the diagnosis of acute pyelonephritis in older patients suspected of infection with unknown focus

BACKGROUND

In older adults, the diagnosis of acute pyelonephritis is challenging because of non-specific symptoms and false-positive urine test results. Few studies have investigated the diagnostic performance of computed tomography (CT) signs.

PURPOSE

To evaluate the diagnostic performance of CT signs for acute pyelonephritis in older patients suspected of infection with unknown focus.

MATERIAL AND METHODS

This cross-sectional study was conducted between 2015 and 2018. Patients aged ≥65 years who underwent blood cultures, urine culture, and non-contrast or contrast-enhanced CT on admission were included. Cases with clinically presumable infection focus before CT were excluded. Two radiologists blinded to clinical information independently reviewed five CT signs: perirenal fat stranding; pelvicalyceal wall thickening and enhancement; renal enlargement; thickening of Gerota's fascia; and area(s) of decreased attenuation. The final diagnoses were made by a clinical expert panel.

RESULTS

Among 473 eligible patients, 61 were diagnosed with acute pyelonephritis. When the laterality of findings between the left and right kidneys were considered, the positive and negative likelihood ratios of perirenal fat stranding were 4.0 (95% confidence interval [CI] = 2.3-7.0) and 0.8 (95% CI = 0.7-0.9) in non-contrast CT, respectively. The other signs in non-contrast CT showed similar diagnostic performance with positive and negative likelihood ratios of 3.5-11.3 and 0.8-0.9, respectively.

CONCLUSION

CT signs can help physicians diagnose acute pyelonephritis in older patients suspected of infection with unknown focus.

Immunoglobulin G4-related Disease of the Genitourinary System: Spectrum of Imaging Findings and Clinical-Pathologic Features

Immunoglobulin G4-related disease (IgG4-RD) is a systemic fibroinflammatory disease characterized by focal or diffuse organ infiltration of IgG4-bearing plasma cells. The diagnosis of IgG4-RD is based on a combination of clinical, serologic, radiologic, and histopathologic findings. IgG4-RD has been reported to affect almost all organ systems. The kidney is the most frequently involved of the genitourinary organs. The most common renal manifestation of IgG4-RD is IgG4-RD tubulointerstitial nephritis, followed by membranous glomerulonephropathy and, less frequently, obstructive nephropathy involving the renal pelvis, ureter, or retroperitoneum. Renal parenchymal lesions may appear as multiple nodular lesions, diffuse patchy infiltrative lesions, or a single nodular lesion. Multiple small nodular cortical lesions are the most common imaging findings of IgG4-RD involving the kidney. Renal pelvic, sinus, or perinephric lesions can also occur. IgG4-RD involvement of other genitourinary organs including the ureter, bladder, urethra, and male and female reproductive organs is rare compared with kidney involvement but may show variable imaging findings such as a localized mass within or surrounding the involved organ or diffuse enlargement of the involved organ. Imaging findings of IgG4-RD involving the genitourinary system are nonspecific but should be differentiated from inflammatory and neoplastic lesions that mimic IgG4-RD. The online slide presentation from the RSNA Annual Meeting is available for this article. ^©RSNA, 2020.

Incidence, risk factors, and clinical outcomes of acute kidney injury associated with acute pyelonephritis in patients attending a tertiary care referral center

Acute kidney injury (AKI) associated with acute pyelonephritis (APN) rarely has been reported. The aim of this study was to evaluate the incidence and risk factors of AKI associated with APN. We retrospectively reviewed the medical records of 403 patients over 18-year old age hospitalized for APN management from October 2009 to September 2014 in tertiary care referral center. Demographic data, clinical symptoms and signs, and laboratory findings were gathered from the medical records and analyzed. The mean age of patients was 57 years and APN commonly occurred in female (87.6%). AKI occurred in 253 patients (62.8%). As per the RIFLE classification, renal injury was graded as ‘Risk’ (62.1%), ‘Injury’ (26.5%), and ‘Failure’ (11.4%). AKI patients were more likely a male gender and had complicated APN. The AKI group had a significantly higher tendency to present with shock. The prevalence of underlying chronic kidney disease (CKD) was significantly higher in the AKI group. There was no difference in mortality between the AKI and non-AKI groups. Multivariate analysis revealed that age over 65 (OR 1.93, 95% CI 1.18–3.13, p= .008), complicated (OR 2.13, 95% CI 1.35–3.34, p= .001) and bilateral APN (OR 1.71, 95% CI 1.01–2.88, p= .045), and initial shock (OR 2.44, 95% CI 1.05–5.71, p= .039) were independent risk factors for the occurrence of AKI in patients with APN. Physicians should attempt to prevent, detect, and manage AKI associated with APN in patients with above conditions.

Bilateral acute non-obstructive pyelonephritis presenting as acute kidney injury requiring haemodialysis

A 54-year-old female patient with hypothyroidism and diabetes mellitus type 2 was brought to emergency room by the family members for acute change in mental status. The laboratory evaluation demonstrated findings consistent with acute renal failure (normal renal function 3 months prior to presentation). She was initiated on hemodialysis due to lack of improvement in renal function. Urine culture done prior to initiation of antibiotics was positive for Escherichia coli, which was later confirmed by renal biopsy. Extensive workup for the cause of renal failure including for connective tissue disease, plasmacytoma, obstruction was negative. She was treated with 6 week course of antibiotics with eventual recovery of her renal function in 4 months.

Are the unenhanced and excretory CT phases necessary for the evaluation of acute pyelonephritis?

Background The most widely accepted computed tomography (CT) protocol for diagnosis of acute pyelonephritis (APN) includes at least a pre- and post-contrast scan, which may expose patients to higher doses of ionizing radiation. Purpose To establish the accuracy, reproducibility, and degree of confidence in CT diagnosis of acute pyelonephritis (APN) and urolithiasis using only images obtained during the nephrographic phase. Material and Methods A retrospective study of 100 consecutive patients (88 women; age range, 19-70 years) with clinical and laboratory suspicion of APN and who underwent triphasic abdominal CT scans (non-contrast, nephrographic, and excretory phases) was performed. Two readers first evaluated independently only the nephrographic phase of scans, and, in a second session, the entire study. The diagnostic reference standard was settled by a third experienced radiologist who reviewed all triphasic scans and clinical data. Results The accuracy of only nephrographic phase for diagnosis of APN and urolithiasis was in the range of 90.3-91.78% and 96.27-99.25%, respectively. There was no significant difference in comparison with the triphasic reading (z: -0.4 - 0.2; P = 0.34-0.83). The average degree of confidence for APN also showed no significant variation for both readers ( P = 0.4 and 0.08). Almost perfect inter-observer agreements for the diagnosis of APN (k = 0.86, P < 0.001) and for urolithiasis (k = 0.84, P < 0.001) were observed when considering only the nephrographic phase. Conclusion CT assessment of APN and urolithiasis can be accurately performed using only the late nephrographic phase, with consequent dose reduction.