Impact of renal replacement therapies on olfactory ability: results of a cross-sectional case control study

Abstract

Introduction Several studies have suggested that chronic kidney disease (CKD) may be associated with olfactory impairment. However, to date, the impact of renal replacement therapies has only been partly defined. Methods We tested the olfactory function of 235 participants [50 kidney transplant recipients (KT), 49 hemodialyzed patients (HD), 30 peritoneal dialysis patients (PD), 51 patients with CKD not on dialysis (ND-CKD) and 55 healthy subjects (HS)] by the Sniffin’ Sticks test (Burghardt®, Wedel, Germany), including the sub-tests for the determination of odor threshold (T), odor discrimination (D), odor identification (I). Each subtest result was then summed up to a composite score, known as the TDI score. The Sino-Nasal Outcome Test-22 (SNOT22), Montreal Cognitive Assessment (MoCA) test and olfactory function Visual Analogue Scale (ofVAS) were also performed. Results The mean TDI score was significantly lower (and consistent with hyposmia), in HD, PD and ND-CKD compared to HS and KT (ANOVA p < 0.001). Similar results were observed in the I and D tests, and with the T score, though with regard to the latter, only in PD and ND-CKD patients. Multiple comparisons among groups demonstrated no significant differences between KT and HS. After adjustments for confounding factors, a significant linear association was found between both urea (β − 0.03, p < 0.003) and eGFR (β 0.08, p < 0.001) with TDI score. No significant association was observed between the TDI score and the ofVAS score (p = 0.293). Conclusions Olfactory impairment affects a large number of CKD patients in the pre-dialysis phase as well as those on dialysis. Kidney transplantation may reverse this condition with a possible positive impact on the quality of life and social behaviors/relationships. Graphic abstract

Olfactory and Gustatory Function before and after Laparoscopic Sleeve Gastrectomy

“…All subjects initially received an MMSE [13] and a SNOT-22 [14], respectively, for cognitive status and sinonasal symptom evaluations. Patients with an MMSE score lower than 18, suggestive of possible severe cognitive deficit, or subjects with a SNOT-22 score higher than 22, indicative of possible sinonasal pathology, were excluded [15]. Other exclusion criteria were diabetes in therapy with insulin [16], hypothyroidism, tobacco smoking (current or in the last 5 years), history of allergic/non-allergic rhinitis or chronic rhinosinusitis, previous sinonasal surgery, history of head trauma or post-viral olfactory loss, and previous chemotherapy/radiotherapy to head and neck [17].…”

Neuroimmunoendocrine Link Between Chronic Kidney Disease and Olfactory Deficits

“…Human olfaction involves complex processes that detect, discriminate, and code thousands of odors ( McGann, 2017 ). Olfactory impairments reflect deficient functionality in the periphery with variable odor thresholds or compromised central processing of the olfactory information resulting in diminished odor discrimination and identification ( Frasnelli et al, 2002 ; Raff et al, 2008 ; Robles-Osorio et al, 2020 ; Iacono et al, 2021 ; Yusuf et al, 2021a ).…”

“…This recovery probably explains the discrepancies observed in odor threshold deficiencies, which improve after dialysis treatment ( Landis et al, 2011 ). The complete recovery of odor discrimination and identification after renal transplantation is due to the decreased generalized inflammation that allows for sufficient neuronal information processing ( Vreman et al, 1980 ; Griep et al, 1997 ; Frasnelli et al, 2002 ; Landis et al, 2011 ; Koseoglu et al, 2017 ; Iacono et al, 2021 ; Yusuf et al, 2021a ). Interestingly, odor stimulation contributes to the recovery of OB atrophy ( Hasegawa-Ishii et al, 2020 ).…”

“…CKD and particularly ESKD patients present significantly decreased olfactory function ( Figure 1 ; Frasnelli et al, 2002 ; Landis et al, 2011 ; Attems et al, 2015 ; Kondo et al, 2020 ; Robles-Osorio et al, 2020 ; Iacono et al, 2021 ; Yusuf et al, 2021a , b ). Additionally, CKD patients follow a controlled diet with reduced calorie uptake, and ∼70% of them suffer from loss of taste ( Frasnelli et al, 2002 ), which can lead to insufficient or unbalanced feeding behaviors.…”

“…Although the straightforward link between impaired olfactory function and the nutritional state is still debatable, poor odor perception is associated with elevated serum urea and a high protein catabolic rate ( Griep et al, 1997 ). The pathological changes underlying the malnutrition-inflammatory state may also contribute to impaired olfactory function in ESKD patients ( Frasnelli et al, 2002 ; Raff et al, 2008 ; Koseoglu et al, 2017 ; Robles-Osorio et al, 2020 ; Iacono et al, 2021 ; Yusuf et al, 2021a ).…”