Functional range of the kidney after a low-severity injury: a randomized study
Authors: Chiglintsev K. A. , Zyryаnov A. V. , Chiglintsev A. Yu. , Makarian A. A. 
Published: July 2023

INTRODUCTION: The basis of renal rehabilitation after trauma is restoration of blood supply and microcirculation processes.

OBJECTIVE: To establish the kidneys’ functional activity indicators in the posttraumatic period using radionuclide diagnostics.

MATERIAL AND METHODS: Verification of severity degree (1–3) and segmental localization of kidney trauma was carried out using radiology methods in 196 patients. Static scintigraphy was used to determine general renal function and its deficit, dynamic scintigraphy was used for renal vascularization (%), glomerular filtration rate, radiopharmaceutical transit in the parenchyma.

The study was conducted in the immediate (up to 30 days) and distant (up to 6 months) periods after the injury.

Statistics: Statistical analysis was performed using Statistica 6/0 software packages; Excel Microsoft Office. Under normal distribution of variables, paired Student’s t-test was used to determine differences between two independent groups. The reliability of accepted statistical estimates was at least 95%.

RESULTS: The findings demonstrate that the volume of parenchyma involved in the injury and the severity of injury determine the functional activity of the kidney. Loss of total kidney function was found when the damage area involved up to 3 segments — 23.7±0.4% in the immediate period after injury, and 16.0±0.4% in the remote period. In cases of parenchymal tears, the loss of total function was 7.1±0.3%, but only in the immediate period after injury. Total blood flow in the compromised organ was significantly affected with injury of 3 segments at the studied follow-up periods, respectively: 34.9±1.0 and 41.8±0.4%. Decrease in GFR was seen in the remote post-traumatic period with maximal contusion zone (38.3±1.6 ml/min) and kidney part destruction (44.4±1.6 ml/min).

DISCUSSION: In case of trauma affecting circulation with development of a local area of ischemia, arterio-venous anastomoses are involved in the preservation of blood flow to intensify the tissue blood flow. Adaptive arterial hyperemia, designed to preserve kidney function, develops. In the case of segment 1 contusion an increase in vascularization and urinary excretion of the injured organ was established. Involvement of a greater volume of parenchyma reduces the probability of blood flow shunting through arterio-venous anastomoses and leads to deepening organ ischemia. Relative decrease in main perfusion pressure is followed by the decrease of its organ component in peritubular capillaries and increase of tubular pressure as evidenced by radionuclide transit data. Correspondingly, there is a decrease of glomerular filtration rate value that is functionally dependent on blood circulation. Restoration of parameters to the normal functional range in the distant period was found only in cases restricted up to 2 damaged parts of the organ parenchyma, and steady degradation of the parameters was leading in the groups with contusion of 3 kidney segments.

CONCLUSION: In case of blunt trauma of the kidney, grade 1 contusion injuries exceeding 1⁄2 the volume of the involved parenchyma entail more severe impairment of renal function than a single non-penetrating tissue ruptures of the 2nd and 3rd grade.