Body Composition, Kidney Size, and Medication Dosing in Acute Kidney Injury: Follow-Up at 90 Days and 12 Months

Acute kidney injury (AKI) is a common and serious condition affecting up to 12% of hospitalized patients, with mortality increasing significantly with severity. Despite the implementation of automated AKI alert systems, clinical outcomes such as hospital length of stay, dialysis need, and death remain suboptimal. This non-interventional, single-center study aims to improve understanding of modifiable factors influencing AKI outcomes by integrating four key components: body composition, kidney size, medication dosing, and patient-reported outcomes.

The primary objective is to assess the prevalence of fluid imbalance, structural kidney abnormalities, and medication errors in patients with AKI Stage 3. It is hypothesized that most patients with AKI are not in a state of euvolemia (i.e., they have either fluid overload or dehydration), that pre-existing chronic kidney disease is detectable via abnormal kidney sonography, and that a significant proportion of patients have medication dosing errors, including inappropriate, contraindicated, or nephrotoxic drugs.

Secondary objectives include evaluating patient awareness of AKI diagnosis, assessing whether patients receive follow-up kidney function monitoring within 90 days after hospital discharge, and identifying gaps in post-discharge care. It is hypothesized that fewer than 100% of patients are aware of their AKI diagnosis, and that a substantial proportion do not undergo follow-up kidney function testing within 90 days.

The study population includes adult patients (≥18 years) with a confirmed diagnosis of AKI Stage 3, defined by an increase in serum creatinine ≥3-fold from baseline or ≥4 mg/dL with an acute rise of ≥0.5 mg/dL, or oliguria (<0.5 mL/kg/h for >6 hours). Patients are identified via the hospital's automated AKI alert system and approached by the nephrology consultative service during hospitalization. Inclusion requires informed consent; exclusion criteria include participation in another clinical trial within the past 4 weeks or a life expectancy of less than 28 days, as judged by the treating physician.

A total of approximately 120 patients are planned for inclusion, with the expectation that around 100 will be available for follow-up at 90 and 365 days post-discharge. Data collection includes electronic health records (Nephro7, SAP) for vital signs, laboratory values, diagnoses, and medication lists. Additional assessments include:

• Body composition analysis using non-invasive bioimpedance spectroscopy (50 frequencies, 5-1000 kHz) to measure total body water, extracellular water, muscle mass, and fat mass. Overhydration (>1000 mL) is a primary outcome.
• Point-of-care ultrasound of the kidneys to assess kidney length (<10 cm), parenchymal thickness (<10 mm), and signs of chronic kidney disease or obstruction. Findings are correlated with estimated glomerular filtration rate (eGFR <45 mL/min).
• Medication review using the national standardized medication plan (Bundesmedikationsplan), supplemented by a joint evaluation by a nephrologist and clinical pharmacist to identify dosing errors, contraindications, or nephrotoxic drugs.

Patients are contacted by telephone at 90 and 365 days after AKI diagnosis to assess:

• Awareness of the AKI diagnosis (Yes/No),
• Perceived severity of the event (Likert scale: 1-5),
• Health literacy regarding AKI (Likert scale: 1-5),
• Whether kidney function (serum creatinine, urea, potassium) was rechecked by their primary care provider within 90 days.

All data are anonymized and stored securely on hospital servers. The study is non-interventional; no changes to standard care are made. The only interventions are the assessments and follow-up calls. The study is ethically approved and conducted in accordance with GDPR and local regulations.

The anticipated benefits include improved patient safety through early detection of fluid imbalance, kidney structural changes, and medication errors. The follow-up calls may prompt overdue kidney function checks by primary care providers. Risks are minimal: potential anxiety from the phone call is mitigated by trained staff and clear communication. The study is considered medically justified as it enhances care quality beyond routine practice.

Data collection concludes with the final follow-up call at 365 days post-AKI alert. Results will inform strategies to improve AKI management, patient education, and post-discharge monitoring, ultimately reducing complications and improving long-term outcomes.

Inclusion criteria

• Age: Adult patients (≥18 years)
• Diagnosis: Confirmed diagnosis of Acute Kidney Injury (AKI) Stage 3, defined by one of the following: Increase in serum creatinine ≥3-fold from baseline, Serum creatinine ≥4 mg/dL with an acute rise of ≥0.5 mg/dL, Oliguria (<0.5 mL/kg/h for >6 hours)
• Informed Consent: Willingness to provide written informed consent for participation in the study

Exclusion criteria

• Participation in another clinical trial: Participation in any other interventional or observational clinical study within the last 4 weeks prior to study enrollment
• Short life expectancy: Clinically assessed life expectancy of less than 28 days by the treating physician
• Inability to consent: Cognitive or language barriers that prevent informed consent or participation in telephone follow-up
• Terminal illness: Active, untreated, or progressive terminal illness (e.g., advanced cancer with no curative intent)
• Inability to follow up: Unavailability of contact information or inability to be reached by telephone at 90 and 365 days post-discharge