Short summary

This project explores the impact of elevated intrarenal pressure (IRP) and intrarenal backflow (IRB) during endoscopic stone surgery on infection risk and kidney function. Using animal models and clinical studies, we assess IRP's role in bacterial translocation, tissue damage, and long-term renal impact. The findings aim to improve surgical safety and identify MRI markers for IRB to guide future clinical practice.

Rationale

Kidney stones are among the most common urological conditions, with a rising global prevalence. Endoscopic treatments such as retrograde intrarenal surgery (RIRS) are increasingly used due to their minimally invasive nature. However, these procedures still lead to complications, particularly infections and potential long-term kidney damage. Elevated intrarenal pressure (IRP) during surgery is a key risk factor, as it causes intrarenal backflow-fluid leakage from the renal pelvis into the bloodstream or surrounding tissues-which can facilitate the spread of bacteria and cause tissue injury. This PhD project aims to investigate the relationship between elevated IRP, intrarenal backflow, and the risk of acute and chronic complications. Specifically, it will evaluate whether MR imaging can non-invasively visualize and quantify backflow, and assess structural and functional kidney changes in patients undergoing repeated endoscopic treatments. The findings will contribute to improved surgical practices and patient safety in modern endourology.

Description of the cohort

Clinical studies: Study II: Participant Population: 10 patients and 10 healthy controls. All patients in the study have undergone treatment at the Department of Urological Surgery, Lillebaelt Hospital, Vejle. Inclusion and Exclusion Criteria for Patients: Inclusion criteria: Adults aged 18-75 years with a history of ≥3 retrograde intrarenal surgeries (RIRS) or ureterorenoscopies (URS) on the affected side, and with at least one month since the most recent procedure on the day of examination. Participants must be legally competent and able to understand the study information. Exclusion criteria: Bilateral stone disease with more than one ureteroscopy on the contralateral ("healthy") side. More than three intrarenal stones at the time of examination or any intrarenal stone larger than 5 mm. Known acute or chronic urinary tract infection (UTI). Multiple percutaneous interventions (PCNL). Known medical kidney disease, including metabolic stone disorders such as cystinuria, renal tubular acidosis, primary hyperoxaluria, nephrocalcinosis, or medullary sponge kidney. Solitary kidney. Presence of MRI-incompatible conditions (e.g., MRI-incompatible implants, claustrophobia). Anatomical variations or focal renal abnormalities that may interfere with analysis (e.g., horseshoe kidney, large or multiple cysts, focal lesions). Pregnancy. Inclusion and Exclusion Criteria for Healthy Controls: Inclusion criteria: Adults aged 35-75 years with normal serum creatinine levels, legally competent and able to understand the study information. Exclusion criteria: Known kidney disease, diabetes, or untreated hypertension. Previous ureteroscopy. Active urinary tract infection or history of upper urinary tract infections. Presence of MRI-incompatible conditions (e.g., MRI-incompatible implants, claustrophobia). Anatomical variations or focal renal abnormalities that may interfere with analysis (e.g., horseshoe kidney, large or multiple cysts, focal lesions). Pregnancy. Study III: Participant population: 12 kidney stone patients scheduled for RIRS (Retrograde Intrarenal Surgery) at the Department of Urological Surgery, Lillebaelt Hospital, Vejle. Inclusion criteria: Patients undergoing RIRS due to a first-time occurrence of non-obstructive kidney stone. Participants must be over 18 years of age, legally competent, and capable of understanding the study information. Exclusion criteria: Patients with metabolic kidney diseases (including cystinuria, renal tubular acidosis, primary hyperoxaluria, nephrocalcinosis, or medullary sponge kidney), fever on the day of surgery, solitary kidney, or anatomical variations or focal kidney abnormalities deemed obstructive to analysis (e.g., horseshoe kidney, large or multiple cysts, focal lesions). Further exclusions include the presence of MRI-incompatible factors (such as MRI-incompatible foreign objects or claustrophobia), ASA physical status classification of 4, and pregnancy.

Data and biological material

Study II: MRI scans, DMSA scintigraphy, blood samples, ultrasound elastography. Study III: Blood samples, MRI scans, intraoperative intrarenal pressure measurements, operation duration, and clinical follow-up at 24 hours and 10 days post-surgery (including blood samples, temperature, blood pressure, pulse, pain score, and information on the use of antibiotics and painkillers)

Collaborating researchers and departments

Department of Urology, Vejle Hospital-a part of Lillebaelt Hospital, University Hospital of Southern Denmark, Vejle, Denmark

• Helene Ulrik Jung
• Søren Kissow Lildal
• Palle Jörn Sloth Osther

MR Research Centre, Aarhus University, Aarhus, Denmark

• Esben Søvsø Szocska Hansen
• Christoffer Laustsen
• Steffen Ringgaard

Department of Clinical Medicine - Department of Radiology, Aarhus University, Aarhus, Denmark

• Ole Graumann
• Sheyanth Mohanakumar

Department of Radiology, Lillebaelt Hospital, Vejle

• Søren Rafael Rafaelsen
• Malene Roland Vils Pedersen

Department of Nuclear Medicine, Lillebaelt Hospital, Vejle

• Henrik Boel Jørgensen