LOIN PAIN IN RARE KIDNEY DISEASE: ANALYSIS OF 3867 QUESTIONNAIRE RESPONSES WITH LINKED DATA FROM THE UK NATIONAL REGISTRY OF RARE KIDNEY DISEASES (RADAR)

Introduction:

Chronic pain is a common symptom for patients with Chronic Kidney Disease (CKD) and reduces health-related quality of life. Loin pain is a predominant feature in certain rare kidney diseases such as Autosomal Dominant Polycystic Kidney Disease. Little is known about loin pain in other rare kidney diseases, including whether loin pain is associated with reduced kidney function, or disease progression. In this questionnaire study we describe the severity and frequency of loin pain in RaDaR participants, and examine associations between loin pain and CKD progression and age at kidney failure.

Methods:

RaDaR participants were invited by email to complete an online questionnaire between 5/3/24-3/6/24. Responses were collated on the JISC online platform. Participants were asked to indicate whether and when they experienced loin pain, analgesic usage, and complete the Short Form McGill Pain Questionnaire (SF-MPQ-2). Responses were linked to RaDaR demographic data, validated data from the UK Renal Registry on Kidney Replacement Therapy (KRT) initiation, and renal unit laboratory data.  Responses were examined individually and by disease type (non-inflammatory, glomerular, cystic, metabolic, tubular, other disorders and Alport syndrome). Baseline characteristics were compared between patients with and without loin pain. Multivariable logistic regression was used to examine associations between loin pain and age, Sex, Ethnicity, Body Mass Index (BMI), Index of Multiple Deprivation Quintile (IMD, an area level measure of deprivation), disease type (baseline=non-inflammatory disorders), and CKD stage/KRT status. Linear regression was used to fit a straight line through each patient’s mean eGFR values for each 3 month period of follow up post diagnosis to determine annualised eGFR slopes for patients with and without loin pain.  

Results:

3867/16431 patients from 31 rare disease groups completed the questionnaire (24% response rate). Loin pain was reported by 62% of respondents, 23% historically and 39% recently (Table1). Respondents who were female (aOR 1.62, 95% CI [1.38-1.90], p<0.001), had a higher BMI (BMI >40, aOR 2.2, [1.39-3.72], p<0.0001), were from more socially deprived areas (IMD Quintile 1-most deprived, aOR 1.75 [1.29-2.37], p<0.001), and had metabolic or cystic kidney disease (aOR 6.1 [2.10-17.7], p<0.001 and aOR 1.72 [1.37-2.15], p<0.001, respectively) had higher odds of loin pain. Ethnicity and CKD stage/KRT status were not associated with increased odds of loin pain (aOR 0.92 [0.80-1.05] p=0.25 and aOR 1.02 [0.98-1.06], p=0.39 respectively). Pain was most frequently reported as aching (79%). Median pain rating index derived from the SF-MPQ-2 was 29, IQR [11-62] for all respondents, and varied by disease type (non-inflammatory disorders median 4, IQR [0-32], metabolic disease 30.5, [9.5-77.5]). 41% of respondents experiencing loin pain used analgesia at least weekly. 4% used strong opioids. Mean annualised eGFR slope over total follow up was -2.8 ml/min/1.73m2/yr (SD 9.0) for participants with loin pain, and -1.9 ml/min/1.73m2/yr (SD 8.4) for those without (p=0.03).

Conclusions:

Loin pain is common in rare kidney diseases: > 60% of participants had experienced loin pain. Loin pain was not associated with CKD stage/KRT status, suggesting it may be related to disease aetiology rather than simply reduced kidney function, but was associated with faster eGFR decline.

I have no potential conflict of interest to disclose.

I did not use generative AI and AI-assisted technologies in the writing process.