Utility of non-enhanced magnetic resonance imaging to detect acute pyelonephritis

Urinary Tract Infection in Children

BACKGROUND

Urinary Tract Infection (UTI) is a common infection in children. Prompt diagnosis and appropriate treatment are very important to reduce the morbidity associated with this condition.

OBJECTIVE

To provide an update on the evaluation, diagnosis, and treatment of urinary tract infection in children.

METHODS

A PubMed search was completed in clinical queries using the key terms "urinary tract infection", "pyelonephritis" OR "cystitis". The search strategy included meta-analyses, randomized controlled trials, clinical trials, observational studies, and reviews. The search was restricted to English literature and the pediatric age group. Patents were searched using the key terms "urinary tract infection" "pyelonephritis" OR "cystitis" from www.google.com/patents, http://espacenet.com, and www.freepatentsonline.com.

RESULTS

Escherichia coli accounts for 80 to 90% of UTI in children. The symptoms and signs are nonspecific throughout infancy. Unexplained fever is the most common symptom of UTI during the first two years of life. After the second year of life, symptoms and signs of pyelonephritis include fever, chills, rigor, flank pain, and costovertebral angle tenderness. Lower tract symptoms and signs include suprapubic pain, dysuria, urinary frequency, urgency, cloudy urine, malodorous urine, and suprapubic tenderness. A urinalysis and urine culture should be performed when UTI is suspected. In the work-up of children with UTI, physicians must judiciously utilize imaging studies to minimize exposure of children to radiation. While waiting for the culture results, prompt antibiotic therapy is indicated for symptomatic UTI based on clinical findings and positive urinalysis to eradicate the infection and improve clinical outcome. The choice of antibiotics should take into consideration local data on antibiotic resistance patterns. Recent patents related to the management of UTI are discussed.

CONCLUSION

Currently, a second or third generation cephalosporin and amoxicillin-clavulanate are drugs of choice in the treatment of acute uncomplicated UTI. Parenteral antibiotic therapy is recommended for infants ≤ 2 months and any child who is toxic-looking, hemodynamically unstable, immunocompromised, unable to tolerate oral medication, or not responding to oral medication. A combination of intravenous ampicillin and intravenous/intramuscular gentamycin or a third-generation cephalosporin can be used in those situations. Routine antimicrobial prophylaxis is rarely justified, but continuous antimicrobial prophylaxis should be considered for children with frequent febrile UTI.

Follow-up of acute pyelonephritis: what causes the diffusion-weighted magnetic resonance imaging recovery to lag clinical recovery?

PURPOSE

To analyze with diffusion-weighted magnetic resonance imaging (DW-MRI) the evolution and progress to resolution of acute pyelonephritis (APN) foci over a period of 3 months after onset.

METHODS

30 women (age 22-51 years) with clinical, laboratory (white blood cell and C-reactive protein), and DW-MRI (4b-values 0, 50, 600, 1000 s/mm²) diagnosis of APN were prospectively enrolled. Two double-blinded radiologists evaluated the number of APN foci, and for each of them dimension (D), absolute diffusion coefficient (ADC), and its ratio R to the ADC of unaffected parenchyma. Signature of radiological recovery was focus no longer visible (DW-) and ADC of its site not inferior to the ADC of the unaffected parenchyma, i.e., R ≥ 0.9. Clinical and DW-MRI follow-ups (FU) were performed at 1 and 3 months.

RESULTS

At the acute stage (t ₀), 187 APN foci were found, with ADC₀ = 1.3 ± 0.2 × 10^-3 mm²/s, R ₀ = 0.65 ± 0.12, and D ₀ = 14 ± 7.5 mm. By the 1-month FU (t ₁), all patients had no symptoms and physiological laboratory values; despite this, only 80 (43%) foci were solved, increasing to 138 (74%) by at the 3-month FU. The ROC curve (AUC ≥ 0.80) identified R ₀ ≤ 0.6 and D ₀ > 15 mm as forecast of slow radiologic resolution. About 80% of foci unsolved at 1 month but with R ₁ ≥ 0.8 and D ₁ ≤ 10 mm reached solution at 3 months.

CONCLUSIONS

DW-MRI recovery of APN foci does not always coincide with clinical recovery. The evolution of an APN focus is shaped by its initial values R ₀ and D ₀. About half of the foci still visible at 1 month reached radiological resolution in the two following months.

Non-enhanced magnetic resonance imaging versus renal scintigraphy in acute pyelonephritis

The utility of non-enhanced magnetic resonance imaging (MRI) has not been examined extensively for diagnosing acute pyelonephritis (APN) in children. The aims of this study were to compare non-enhanced MRI with technetium-99 m dimercaptosuccinic acid (^99m Tc-DMSA) renal scintigraphy in detecting APN. Six boys and one girl with temperature ≥38°C and positive urine culture received both non-enhanced MRI with whole body diffusion-weighted imaging (DWI) and ^99m Tc-DMSA scintigraphy ≤7 days from the fever onset. The sensitivity and specificity of MRI in detecting APN lesions diagnosed on ^99m Tc-DMSA scintigraphy were 80% and 100%, respectively. Non-enhanced MRI in children with suspected APN ≤7 days from fever onset might be a suitable replacement for ^99m Tc-DMSA scintigraphy for the detection of APN.

Magnetic Resonance Imaging of Abdominal and Pelvic Pain in the Pregnant Patient

The utility of MR imaging in evaluating abdominal and pelvic pain in the pregnant patient is discussed. Details regarding the indications, technical aspects, and imaging findings of various common abdominal and pelvic abnormalities in pregnancy are reviewed.

Acute pyelonephritis in transplanted kidneys: can diffusion-weighted magnetic resonance imaging be useful for diagnosis and follow-up?

PURPOSE

To assess reliability of diffusion-weighted magnetic resonance imaging (DW-MRI) in the management of acute pyelonephritis (APN) foci in transplanted kidneys.

MATERIALS AND METHODS

In the 2012-2014 period, 24 kidney-transplanted patients underwent MR screening for clinical suspicion of APN. Two readers independently analyzed all images, establishing presence and location of APN foci. The 22 patients who were positive at the MR exam constituted the study population. For each patient the apparent diffusion coefficient (ADC) was measured in the APN foci and in three sites of the healthy parenchyma (case-control comparison). The data were matched to the laboratory measurements for white blood cell, C-reactive protein, and serum creatinine.

RESULTS

Forty-six APN foci were found in 22/24 patients. At the acute stage, the difference in ADC between healthy parenchyma and APN foci was significant (2.06 ± 0.16 vs. 1.43 ± 0.32 × 10(-3) mm(2)/s; p < 0.0001). The performance of ADC as APN indicator was tested by the receiving operating characteristics (ROC) curve: the area under curve AUC = 0.99 witnessed an excellent discriminatory ability, with threshold APN/normal parenchyma 1.9 × 10(-3) mm(2)/s. At the 1-month follow-up 43/46 APN foci were no longer visible, with ADC values significantly higher than at the acute stage; all laboratory data were physiological, with WBC significantly reduced from the acute phase (5.2 ± 1.6 × 10(9)/L vs. 10.6 ± 4.8 × 10(9)/L; p < 0.0001). The other 3 patients underwent further therapy and exams, including a third MR.

CONCLUSIONS

DW-MRI with ADC measurement seems to be a reliable tool in diagnosing and monitoring APN foci in transplanted kidneys, with clinical impact on patient management.

[Infectious diseases and injuries of bladder and urinary tract]

Urinary tract infections are the most common infectious diseases in Germany. In most cases clarification does not rely on imaging techniques other than sonography and is made mostly based on clinical symptoms. Computed tomography (CT) and magnetic resonance imaging (MRI) can be used in selected cases to find the cause and detection or exclusion of complications, e.g. recurrent or atypical and complicated courses. The method of choice for clarification of urolithiasis is CT. Using low-dose techniques, detection or exclusion of urinary stones can be achieved with a high sensitivity and specificity as well as an acceptable level of radiation exposure. Native stone CT supplies additional fundamental information that can substantially influence further therapy planning. The diagnosis of ureteral injuries is clinically and radiologically not trivial and clarification is aided by urographic contrast media. The method of CT cystography has an important role in the diagnostics of urinary bladder injuries.