A comprehensive renal injury concept based on a validated finite element model of the human abdomen.

BACKGROUND: The identification of abdominal injury mechanisms, development of effective countermeasures, and refinement of clinical approach to injury treatment are greatly facilitated by the employment of numerical models that can predict injuries resulting from complicated soft tissue interactions during blunt abdominal impact. METHODS: The present study introduces a detailed three-dimensional finite element model of the human abdomen that was developed specifically for the investigation of renal trauma. The model geometry and materials reflect the complex mechanical environment of the abdomen, and is validated against both published and novel experiments. RESULTS: It is shown that use of the proposed model, in combination with appropriate mechanical organ injury criteria, provides a significant step toward a comprehensive renal injury concept. Specifically, the abdominal model offers the possibility to investigate injury likelihood and identify injury mechanisms over a broad range of impact loading scenarios. CONCLUSIONS: A sophisticated numerical model of renal trauma has been developed that can be used to effectively predict renal injury outcome for lateral impact.

Low-dose versus standard-dose CT protocol in patients with clinically suspected renal colic.

OBJECTIVE: The purpose of our study was to compare a low-dose abdominal CT protocol, delivering a dose of radiation close to the dose delivered by abdominal radiography, with standard-dose unenhanced CT in patients with suspected renal colic. MATERIALS AND METHODS: One hundred twenty-five patients (87 men, 38 women; mean age, 45 years) who were admitted with suspected renal colic underwent both abdominal low-dose CT (30 mAs) and standard-dose CT (180 mAs). Low-dose CT and standard-dose CT were independently reviewed, in a delayed fashion, by two radiologists for the characterization of renal and ureteral calculi (location, size) and for indirect signs of renal colic (renal enlargement, pyeloureteral dilatation, periureteral or renal stranding). Results reported for low-dose CT, with regard to the patients' body mass indexes (BMIs), were compared with those obtained with standard-dose CT (reference standard). The presence of non-urinary tract-related disorders was also assessed. Informed consent was obtained from all patients. RESULTS: In patients with a BMI < 30, low-dose CT achieved 96% sensitivity and 100% specificity for the detection of indirect signs of renal colic and a sensitivity of 95% and a specificity of 97% for detecting ureteral calculi. In patients with a BMI < 30, low-dose CT was 86% sensitive for detecting ureteral calculi < 3 mm and 100% sensitive for detecting calculi > 3 mm. Low-dose CT was 100% sensitive and specific for depicting non-urinary tract-related disorders (n = 6). CONCLUSION: Low-dose CT achieves sensitivities and specificities close to those of standard-dose CT in assessing the diagnosis of renal colic, depicting ureteral calculi > 3 mm in patients with a BMI < 30, and correctly identifying alternative diagnoses.

Abdominal plain film in patients admitted with clinical suspicion of renal colic: should it be replaced by low-dose computed tomography?

OBJECTIVES: To evaluate a low-dose abdominal computed tomography (LDCT) protocol, delivering a radiation dose close to that delivered by an abdominal plain film (APF), in patients with a clinical suspicion of renal colic. METHODS: A total of 139 patients for whom an APF was requested for suspicion of renal colic were randomized into two groups. The patients in group 1 (n = 68) underwent an admission LDCT scan delivering a 2.1-mSv radiation dose to women and 1.6 mSv to men, instead of the APF. Patients in group 2 (n = 71) underwent an APF. Clinical and radiologic follow-up data were obtained for each patient. The number of additional abdominal ultrasound and CT scans performed to reach a confident final diagnosis and determine the proper treatment was compared between the two groups. A mean effective radiation dose was obtained in each group. RESULTS: Of the 68 patients in group 1 (LDCT), 10 (15%) underwent ultrasonography, 9 (13%) conventional abdominal CT, and 2 (3%) both. In group 2 (APF), the corresponding percentages were 27% (19 of 71), 28% (20 of 71), and 23% (16 of 71). Of the 68 patients in group 1, 47 (69%) did not require any additional examinations compared with 16 (23%) of the 71 patients in group 2 (P < 0.0001). The mean effective dose was 3.5 and 6.9 mSv in groups 1 and 2, respectively (P < 0.0001). CONCLUSIONS: In patients with suspicion of renal colic, replacing the admission APF with our LDCT protocol will significantly reduce the need for additional CT or ultrasonography. Also, our LDCT protocol decreases by almost 50% the mean radiation dose per patient.

Cryosurgical changes in the porcine kidney: histologic analysis with thermal history correlation.

Advances in minimally invasive renal cryosurgery have renewed interest in the relative contributions of direct cryothermic and secondary vascular injury-associated ischemic cell injury. Prior studies have evaluated renal cryolesions seven or more days post-ablation and postulated that vascular injury is the primary cell injury mechanism; however, the contributions of direct versus secondary cell injury are not morphologically distinguishable during the healing/repair stage of a cryolesion. While more optimal to evaluate this issue, minimal acute (< or = 3 days) post-ablation histologic data with thermal history correlation exists. This study evaluates three groups of porcine renal cryolesions: Group (1) in vitro non-perfused (n = 5); Group (2) in vivo 2-h post-ablation perfused (n = 5); and Group (3) in vivo 3-day post-ablation perfused (n = 6). The 3.4 mm argon-cooled cryoprobe's thermal history included a 75 degrees C/min cooling rate, -130 degrees C end temperature, 60 degrees C/min thawing rate, and 15-min freeze time. An enthalpy-based mathematical model with a 2-D transient axisymmetric numerical solution with blood flow consideration was used to determine the thermal history within the ice ball. All three groups of cryolesions showed histologically similar central regions of complete cell death (CD) and transition zones of incomplete cell death (TZ). The CD had radii of 1.4, 1.1, and 1.0 cm in the non-perfused, 2-h and 3-day lesions, respectively. Capillary thrombosis was present in the 2-h perfused cryolesions with the addition of TZ arteriolar/venous thrombosis in the 3-day perfused lesions. Thermal modeling revealed the outer CD boundary in all three groups experienced similar thermal histories with an approximately -20 degrees C end temperature and 2 degrees C/min cooling and thawing rates. The presence of similar CD histology and in vitro/in vivo thermal histories in each group suggests that direct cryothermic cell injury, prior to or synchronous with vascular thrombosis, is a primary mediator of cell death in renal cryolesions.