Older adult patients with acute-onset minimal change nephrotic syndrome (MCNS) often have difficulties with exercise therapy due to uremia caused by severe generalized edema and acute kidney injury (AKI). Rehabilitation treatment targeting increased light-intensity physical activity (LPA) is typically implemented to address this limitation. An 81-year-old man with suspected MCNS complicated by stage I AKI was admitted to our hospital. The patient’s short physical performance battery (SPPB) score was 10 points, while his total physical activity (TPA) was 411 steps per day. To increase his LPA, the patient performed resistance exercises in the sitting position and standing activities with support under supervision five times per week at low load and high frequency. Physical activity education with self-monitoring using an activity meter and check sheet was also implemented during the unmonitored periods. After uremia and other symptoms improved, aerobic and resistance exercises were added. At discharge, the patient’s moderate-vigorous physical activity (MVPA) increased from 0.1 to 3.2 minutes per day; his LPA increased from 5.1 to 34.6 minutes per day; and his TPA increased from 411 to 3,233 steps per day. His SPPB score improved from 10 to 12 points, while the motor component of the functional independence measure (FIM) increased from 66 to 82 points, leading to improved activities of daily living (ADL). These results indicate that LPA-focused rehabilitation treatment in older patients with MCNS and AKI is both effective and feasible, potentially contributing to improved physical activity and ADL and facilitating the transition to exercise therapy after clinical improvement.
Minimal change nephrotic syndrome (MCNS) accounts for approximately 20% of cases of nephrotic syndrome (NS) in older adults [1, 2]. Although generally responsive to steroid therapy, frequent relapses are common [3]. Acute kidney injury (AKI) complicates about 40% of adult cases of MCNS [4]. Fluid overload and uremia associated with MCNS and AKI contribute to reduced physical activity, decline of physical function, and impairment of activities of daily living (ADL). Furthermore, steroid-induced myopathy accelerates functional deterioration and worsens ADL impairment [5, 6]. Such a decline diminishes social participation, lowers quality of life, increases healthcare costs, and imposes additional burdens on caregivers, highlighting the need for effective rehabilitation in older adults with NS.
According to Japanese renal rehabilitation guidelines, active exercise is not recommended for patients with MCNS [7], although recent reports suggest that early rehabilitation treatment can be both effective and safe in patients with NS under stable general conditions [6, 8, 9]. Nevertheless, optimal rehabilitation strategies remain unclear for patients presenting with uremia who are unable to tolerate conventional exercise therapy. Low-intensity physical activity (LPA), defined as 1.5–2.9 metabolic equivalents (METs), may represent a feasible alternative in this population [10]. LPA includes activities such as slow walking, light seated movements, and housework, which together account for a substantial proportion of total physical activity (TPA) in older adults with age-related decline [11].
In addition to high-intensity exercise (≥3 METs), reducing sedentary time and increasing LPA have been shown to help prevent physical function decline in healthy older adults [10]. Interventions aimed at promoting LPA and reducing sedentary behavior are both feasible and beneficial in older populations [12, 13]. Thus, even in MCNS patients complicated by AKI for whom conventional exercise therapy is not feasible due to factors such as uremia, increasing LPA may help maintain physical function and TPA, thereby mitigating the impairment of ADL. This case report describes an older adult with MCNS complicated by AKI whose physical function and TPA improved through an intervention designed to increase LPA.
The patient was an 81-year-old man with a history of hypertension and valvular heart disease, including mild aortic stenosis, aortic regurgitation, mitral regurgitation, and trivial tricuspid regurgitation. He was independent in activities of daily living (ADL), drove independently, and managed a dry-cleaning business prior to admission. Approximately two months before hospitalization, he developed bilateral lower extremity edema. Diuretic therapy was initiated but was ineffective. Subsequently, he experienced nausea, vomiting, anorexia, and fatigue. Abdominal computed tomography (CT) revealed severe left-sided hydronephrosis with cortical thinning caused by ureteral calculi. On hospital day 5, laboratory evaluation showed marked hypoalbuminemia (serum albumin 1.6 g/dl) and heavy proteinuria (10.7 g/day), consistent with nephrotic syndrome (NS). A urinary protein selectivity index of 0.11 suggested minimal change nephrotic syndrome (MCNS). Renal biopsy was not feasible due to the presence of a solitary functional right kidney with a lower-pole cyst.
At admission, the patient’s serum creatinine (sCr) was 1.81 mg/dl and did not improve following resolution of hydronephrosis after left ureteral stent placement. From hospital day 4 to 6, his sCr increased from 2.10 mg/dl to 3.40 mg/dl. His blood urea nitrogen (BUN) on admission was 58.0 mg/dl, and his urine output ranged from 200 ml/day to 800 ml/day during the two weeks after admission, indicating oliguria. According to the Kidney Disease: Improving Global Outcomes (KDIGO)—an international nonprofit consortium that issues evidence-based nephrology guidelines—the patient met the criteria for KDIGO stage 1 AKI, based on a ≥1.5-fold increase in sCr from baseline within seven days [14].
The results of the assessment of physical function before rehabilitation are summarized in Table 1. We used the Short Physical Performance Battery (SPPB; 0–12, higher=better; balance, 4-m gait speed, five-times sit-to-stand) and the Functional Independence Measure (FIM; 18 items, scored 1–7; total 18–126 with motor and cognitive subscales; higher=more independent) [15, 16]. From hospital day 1 (day of admission), the patient was unsteady and required an escort to walk to the toilet. On hospital day 6, the patient’s physical function results were as follows: weight, 63.5 kg; isometric knee extension strength to body weight ratio (IKES/BW), 0.37 kgf/kg on the right and 0.39 kgf/kg on the left; 10-m walk test (10MWT) speed, 0.47 m/s; SPPB, 10 points; FIM, 101 points; FIM breakdown, 66 points for motor items and 35 points for cognitive items; assistance was required for motor items. The patient wore a physical activity meter (Lifecorder GS, Suzuken) to measure the average amount and duration of physical activity over a week: his light-intensity physical activity (LPA) was 5.1 minutes/day, moderate-to-vigorous physical activity (MVPA) was 0.1 minutes/day, and total physical activity (TPA) was 411 steps.
| At the time of admission | At the time of discharge | |
|---|---|---|
| BW (kg) | 63.5 | 43.2 |
| IKES/BW (kgf/kg) | 0.37/0.39 | 0.52/0.49 |
| 10MWT (m/sec) | 0.47 | 1.13 |
| SPPB (points) | 10 | 12 |
| FIM (points) | 101 | 112 |
| LPA (min/day) | 5.1 | 34.6 |
| MVPA (min/day) | 0.1 | 3.2 |
| TPA (steps/day) | 411 | 3,233 |
BW decreased from 63.2 kg at admission to 43.2 kg at discharge. IKES/BW was below the 0.40 kgf/kg threshold for independent ambulation at admission but exceeded this benchmark following rehabilitation therapy. The 10MWT time, SPPB score, and FIM score were low at admission but improved by discharge. LPA time increased from 5.1 to 34.6 minutes, MVPA time increased from 0.1 to 3.2 minutes, and TPA, measured by step count, increased from 411 to 3,233 steps. BW: body weight, IKES/BW: isometric knee extension strength to body weight ratio, 10MWT: 10-meter walk test, SPPB: short physical performance battery, FIM: Functional Independence Measure, LPA: light-intensity physical activity, MVPA: moderate-to-vigorous physical activity, TPA: total physical activity.
The patient’s pharmacologic treatment is summarized in Figure 1. Considering the patient’s advanced age and risk of infection, methylprednisolone 500 mg/day was administered for three days in combination with cyclosporine 100 mg/day. Blood concentration monitoring was performed to maintain trough levels (C0) <100 ng/ml and 2-hour post-dose levels (C2) within 600–900 ng/ml. During therapy, cyclosporine was continuously administered at 75–100 mg/day. Heparin was initiated for thromboprophylaxis and later transitioned to warfarin, with dose adjustment normalizing a transiently prolonged PT-INR (1.25). Fluid management with furosemide and trichlormethiazide resulted in weight reduction and improvement of uremia.
The patient was elderly and had a high risk of infection associated with long-term steroid administration, and thus, CyA administration was started after 3 days of half-pulse therapy. In addition, HEPA and WF were administered for thrombosis prevention, and fluid body management was centered on FURO. The left vertical axis represents Methylprednisolone, and the right vertical axis represents cyclosporine. mPSL: methylprednisolone, CyA: Cyclosporine, FURO: Furosemide, TCM: Trichlormethiazide, HEPA: Heparin, WF: Warfarin, DW: Drug Withdrawal, BW: Body Weight, FI: Food Intake
Rehabilitation treatment was initiated on hospital day 5. Because fluid retention and uremia limited the feasibility of moderate-to-vigorous physical activity (MVPA), low-intensity physical activity (LPA) – including seated resistance and supported standing exercises – was introduced. Supervised low-load, high-frequency training was conducted five times per week. To promote LPA during unsupervised time, physical activity education and self-monitoring using a step counter and check sheet were implemented to encourage behavior change [13, 17, 18]. Baseline activity was defined as the first week’s average, and the daily target was set at 500–1,000 steps, according to Japanese renal rehabilitation guidelines [7]. If the weekly goal was achieved, the target was increased by 500 steps. Daily feedback on step count and goal attainment was provided. By hospital day 30, improvement in uremia allowed the introduction of MVPA, including aerobic exercise on a bicycle ergometer and resistance training (e.g., calf raises and squats). Aerobic exercise was prescribed using the Karvonen method, starting at 40% intensity for 10 minutes and gradually increasing to 60% for 20 minutes. Resistance training was performed at an intensity of 3–5 on the modified Borg scale for 10–20 minutes, in three sets of 10–20 repetitions.
Changes in the patient’s physical activity, physical function, and ADL are shown in Table 1. On hospital day 42, his physical activity increased to 34.6 min/day for LPA, 5.1 min/day for MVPA, and 3,233 steps/day for TPA (Figure 2). His physical function/ADL improved: weight 43.2 kg; IKES/BW, 0.52 kgf/kg on the right and 0.49 kgf/kg on the left; 10MWT 1.13 m/s; SPPB 12; FIM-motor 112. Biochemistry: Alb 1.6 g/dl, urinary protein 4.19 g/day, sCr 2.11 mg/dl, BUN 48.9 mg/dl. Although classified as steroid-resistant, incomplete-remission type I MCNS, these parameters did not worsen with training, and no rehabilitation-related adverse events occurred (Figure 3 and 4). Nephrotic syndrome persisted, but no rehabilitation-induced exacerbation was observed.
TPA: Total Physical Activity, LPA: Light-Intensity Physical Activity, MVPA: Moderate-Vigorous Physical Activity
A transient increase in BUN was observed during hospitalization, but no adverse events were reported. The left vertical axis shows BUN, and the right vertical axis shows. sCr: Serum Creatinine, BUN: Blood Urea Nitrogen.
Alb levels remained low throughout the hospitalization period; UP levels fluctuated during the hospitalization period. Alb: Serum Albumin, UP: Urine Protein.
This case suggests that, in an older adult with MCNS complicated by AKI, raising light-intensity physical activity (LPA) improved physical function (SPPB), total activity (steps), and independence (FIM). Education with activity meters and feedback sheets effectively promoted LPA. Importantly, renal indices (sCr, urinary protein, Alb) did not worsen, and no adverse events occurred, indicating safety. Clinically meaningful gains were achieved despite limited exercise capacity. LPA therefore appears to be a practical, low-risk strategy to boost activity and mitigate progression of acute disuse syndrome in similar patients.
A combined intervention of physical activity education and self-monitoring promoted behavior change and increased LPA. Prior studies recommend enhancing daily activities, especially walking, to raise LPA [19]. Interventions integrating self-monitoring with an activity monitor, feedback, and education increase activity and help to establish physical activity habits [20–22]. In the present case, education explained LPA methods and benefits – seated resistance and supported standing – and used strategies to strengthen understanding and self-efficacy (SE), encouraging behavior change [23, 24]. This likely contributed to greater LPA time, step count, and physical function during unsupervised periods. Consistent with earlier research, combining a monitor with a step-count check sheet visualized daily activity, supporting SE maintenance and reinforcing change [25–27]. Recently, Snacktivity™ – frequent, simple movements accumulating to ≥150 minutes/week – has been proposed [28–31]. Such small, easily implemented behaviors may be more sustainable than complex programs because they require minimal preparation, planning, or equipment [32–34]. In this case, incorporating seated self-training resembling Snacktivity™ may have enhanced adherence during unsupervised time and contributed to the overall increase in LPA.
In this case, an 81-year-old patient with uremia struggled with conventional rehabilitation treatment, yet increases in TPA—particularly LPA—were associated with gains in physical function and ADL. Performing LPA may have limited the disuse syndrome and enabled later, more intensive therapy as the patient’s condition improved. Prior studies have shown that LPA improves physical function in healthy older adults (~70 years) and in frail elders [35, 36]. Similarly, the observed LPA increase likely aided both function and ADL. The mechanisms likely include enhanced muscle strength and metabolic adaptations.
Light-intensity activity, including seated resistance and supported standing, was emphasized. Such exercise preferentially recruits smaller motor units, then larger ones, increasing strength [37]. It may also promote hypertrophy, myofibrillar protein synthesis, and intracellular signaling, improving muscle and overall activity [37]. Moreover, step count, standing time, and sedentary behavior correlate with function in adults ≥75 years with limited MVPA [38]. Here, encouraging unsupervised seated/standing self-training likely reduced sedentary time and raised overall activity, supporting maintenance and improvement of function and ADL. These findings support the use of LPA as a practical initial step in other, similar cases.
Although this patient did not show marked improvement in urinary albumin protein owing to his steroid-resistant MCNS, he was able to carry out rehabilitation treatment without worsening renal function. The exercise intensity of LPA corresponds to 20–39% of peak oxygen uptake (Peak VO2) or heart rate reserve (HRR), and 40–63% of maximal heart rate (HRmax), indicating light intensity [39]. Such light-intensity exercise has been reported to address safety concerns and improves adherence [37]. LPA has also been reported to be accessible to patients who are unable to perform high-intensity workouts, making it a feasible option for maintaining physical function and quality of life [40]. Considering these findings, rehabilitation treatment using LPA under appropriate monitoring may be safely implemented even in older adults with MCNS complicated by AKI.
This report has limitations. First, it describes a single patient, limiting generalizability; the efficacy and safety of LPA in other MCNS/AKI populations remain uncertain. Larger series across ages and clinical backgrounds are needed. Second, causality cannot be inferred without a comparator. Because this was a single-group intervention, the observed changes may reflect natural recovery, concurrent treatments, or measurement variability rather than the LPA-focused program. Third, long-term effects and durability were not assessed. Outcomes were evaluated only through hospital discharge; whether benefits persist, remit, or translate to reduced relapse, rehospitalization, or functional decline is unknown. Future studies should include controlled designs, longer follow-up, and structured post-discharge education and self-monitoring to test sustainability. Multicenter cohorts with standardized protocols, blinded outcome assessment, and objective activity monitoring (accelerometry) would strengthen inference. Prespecified renal endpoints (sCr, eGFR slope, proteinuria) and adverse-event surveillance are also warranted. Cost and feasibility should be examined.
Interventions aimed at increasing LPA in elderly patients with MCNS complicated by AKI may help prevent the progression of disuse syndrome in the acute phase, thereby facilitating the transition to exercise therapy and contributing to improvements in physical function and ADL. Such interventions targeting an increase in LPA may represent an effective and feasible therapeutic strategy.
We thank the patient and all doctors involved in this case.
This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.
Not applicable.
Written informed consent was obtained from the patient for publication of this case report along with any accompanying images.
Conceptualization: Yuma Hirano
Methodology: Tomoya Omura, Yuma Hirano
Formal analysis and investigation: Tomoya Omura, Yuma Hirano
Data curation: Tomoya Omura, Yuma Hirano, Tomoya Yamaguchi, Iori Suganuma, Sayaka Ishigaki, Shunji Takashima, Katsuya Yamauchi
Writing – original draft: Tomoya Omura, Yuma Hirano
Writing – review & editing: Tomoya Omura, Yuma Hirano, Tomoya Yamaguchi, Iori Suganuma, Yuichi Tawara, Sayaka Ishigaki, Shunji Takashima, Katsuya Yamauchi
Visualization: Tomoya Omura, Yuma Hirano, Tomoya Yamaguchi, Iori Suganuma, Yuichi Tawara, Sayaka Ishigaki, Shunji Takashima, Katsuya Yamauchi
Resources: Yuma Hirano, Tomoya Yamaguchi, Iori Suganuma, Sayaka Ishigaki, Shunji Takashima, Katsuya Yamauchi
Supervision: Yuma Hirano, Tomoya Yamaguchi, Iori Suganuma, Yuichi Tawara, Sayaka Ishigaki, Shunji Takashima, Katsuya Yamauchi
All data generated or analyzed during this study are included in this published article (and its supplementary files).
The authors declare that they have no conflict of interest.
