|Year : 2016 | Volume
| Issue : 1 | Page : 4-9
Proportion of hearing loss in chronic renal failure: Our experience
EK Reddy1, DR Surya Prakash1, Manda G. K. D. Rama Krishna2
1 Department of ENT, M.S. Ramaiah Medical College, Bengaluru, Karnataka, India
2 Department of ENT, Varma Hospital, Bhimavaram, Andhra Pradesh, India
|Date of Web Publication||16-Feb-2016|
D R Surya Prakash
Department of ENT, M.S. Ramaiah Medical College, MSR Nagar, Bengaluru - 560 054, Karnataka
Source of Support: None, Conflict of Interest: None
Introduction: This study is taken up to study the magnitude of sensorineural hearing loss (SNHL) in chronic kidney disease (CKD) patients. Two hundred patients (400 ears) who had CKD 5 and all patients underwent hemodialysis were taken into study. Methods: All patients had clinical ENT examination and audiological evaluation with pure tone audiometry and impedance audiometry. All patients had SNHL. Results: In summary, high frequencies are affected in 52%, middle frequencies in 9%, and low frequencies in 2.5% of individuals. About 2.5% of patients had hearing loss in all frequencies. Hearing loss is observed only at 8000 Hz in 10% of individuals. Among all patients, 21 patients (42 ears) underwent a renal transplant, and post-transplant duration was about 1 year, 11 patients (57%) having hearing loss. Thus, hearing loss was found in 122 (61%) members bilaterally. Unilateral hearing loss is present in 5 (2.5%) patients. Conclusion: Hearing loss is present in 63.5% individuals (249 out of 400 ears). Thus, SNHL is present in 63.5% in patients with chronic renal failure and severity correlated with duration of disease. No correlation between other covariables.
Keywords: Chronic kidney disease, Hemodialysis, High-frequency hearing loss, Renal transplant, Sensorineural hearing loss
|How to cite this article:|
Reddy E K, Surya Prakash D R, Rama Krishna MG. Proportion of hearing loss in chronic renal failure: Our experience. Indian J Otol 2016;22:4-9
|How to cite this URL:|
Reddy E K, Surya Prakash D R, Rama Krishna MG. Proportion of hearing loss in chronic renal failure: Our experience. Indian J Otol [serial online] 2016 [cited 2020 Feb 25];22:4-9. Available from: http://www.indianjotol.org/text.asp?2016/22/1/4/176503
| Introduction|| |
Sensorineural hearing impairment has been reported in chronic renal failure (CRF) patients with a prevalence of 20–40%. The etiopathogenetic mechanisms reported included osmotic alteration resulting in loss of hair cells, collapse of the endolymphatic space, edema and atrophy of specialized auditory cells and in some, complications of hemodialysis.
There also are certain anatomic similarities at an ultra-structural level and evidence for similar antigenicity of the cochlea and kidney.,, Multiple shared risk factors for chronic kidney disease (CKD) and hearing loss include age, diabetes, hypertension, and medications that are both ototoxic and nephrotoxic. Moreover, in patients with established CKD, multiple risk factors have been hypothesized to cause hearing loss, including the use of ototoxic medications, hypertension, and diabetes, particularly in association with hypertension, electrolyte disturbances, and hemodialysis itself.,, Hence, this study has been taken up to determine the magnitude of hearing loss in CRF patients.
- To determine proportion and pattern of sensorineural hearing loss (SNHL) among patients with renal disease attending Nephrology Outpatient Department (OPD), M.S. Ramaiah Hospitals
- To study the association between demographic characteristics and degree of hearing loss.
Review of literature
Johnson and Mathog noted high frequency hearing loss in 61 adults early in the course of hemodialysis. Mancini et al. reported hearing loss in 47.5% of patients with congenital disease and in 21% of children with acquired renal disease. Henrich et al. found that 75% of the patients showed no deterioration of hearing found that 75% of the patients showed no deterioration of hearing during the 4-year period of follow-up. They concluded that hearing loss is common in renal failure, but it does not worsen with duration of treatment.,
| Materials and Methods|| |
Estimated sample size was 200. A total of 200 patients were enrolled in the study between October 2011–June 2013. Informed consent was taken from all patients for participation in the study. The sample size has been estimated in consultation with a biostatistician based on evidence from the study, which revealed the proportion of hearing loss among patients having renal disease was 67% in hospital setting. Assuming relative precision 10%, confidence level 95%, data loss 15%, and the sample size estimated with N Master software (Department of Biostatistics, CMC, Vellore) is 200. Two hundred patients diagnosed with CKD, attending outpatient clinic will be recruited based on the inclusion and exclusion criteria mentioned below.
All cases diagnosed as CRF. They will be staged according to following criteria [Table 1].
Patients younger than 15 years of age, who have undergone prior ear surgery, patients with tympanic membrane perforation, tympanosclerosis, and otosclerosis, patients above 56 years of age (to exclude presbycusis).
Pure tone audiometry, impedance audiometry. Nephrological investigations such as serum creatinine, blood urea nitrogen (BUN), and serum electrolytes.
Hearing-related questions included family history of hearing loss, past medical or surgical treatment of otologic conditions, diseases associated with hearing loss, and risk factors for ear disease. Other questions addressed exposure to noise at work.
These cases were evaluated in Nephrology Unit and ENT OPD. Cases with past history of hearing loss, ear discharge, diabetes, and hypertension were not included in the study. Thereafter, all patients were subjected to basic tests of renal function hemoglobin, hematocrit, blood urea, serum creatinine, and BUN). Pure tone audiometry and impedance audiometry were performed by qualified audiologists in sound-treated booths using standard TDH-50P, B 17 headphones, and interacoustics AAA22 audiometer calibrated regularly to AIISH standards. Impedance audiometry with reflexes done at same sitting. All patients had baseline audiological evaluation with pure tone audiometry. Pure tone audiometry was performed for both air conduction and bone conduction for 250, 500, 1000, 2000, 4000, 8000 Hz. Because bone conduction hearing testing is limited to 4000 Hz, measurements ≥4000 Hz were performed using air conduction testing alone. The sensorineural hearing at high frequencies (8000 Hz) tested by air conduction is unaffected by, and independent of, middle ear effusion.
Patients divided into three age groups (15–30, 31–45, 46–55), duration of disease in to two groups (<5, ≥5 years), hemodialysis into two groups (<3 years, ≥3 years). All three variables compared with hearing loss. Hearing loss divided according to pure tone average, mild, moderate, moderately severe, severe, and profound. Also divided according to frequencies involved into low, middle, and high frequencies [Table 2].
WHO (1980) recommended above classification on the basis of pure tone audiogram taking an average of thresholds of hearing frequencies 500, 1000, 2000 Hz with reference to ISO: R. 389-1970. Descriptive statistical analysis has been carried out in this study. Results on continuous measurements are presented on mean ± standard deviation (minimum-maximum) and results on categorical measurements are presented in number (%). Chi-square test is used to compare the difference in proportions. The significance is assessed at 5% level of significance. The statistical software SPSS 18.0 (SPSS Inc., Chicago, IL) was used for the analysis of the data and Microsoft Word and Excel have been used to generate graphs, tables, etc.
| Results|| |
Proportion of hearing loss in patients of CRF (200 patients) to study the quantification of magnitude of SNHL. This is a cross-sectional study. The study population included 143 men (71.5%) and 57 women (28.5%). This is cross-sectional study 200 patients diagnosed with CRF (CKD Grade-5) attending Nephrology OPD, M.S. Ramaiah Hospitals.
Two hundred CRF patients treated with hemodialysis included in the study. This included 143 males and 57 females. Age range was 15–55 years (mean of 39.71). Duration of illness 1–9 years (mean 6.4). Duration of hemodialysis was 1–6 years (mean 3.17). The diastolic blood pressure (BP) was between 90 and 110 mmHg (mean 103.64). The patients were on a daily dose of diuretic (furosemide) between 40 and 200 mg (mean 102.42). Patients using aminoglycosides excluded from the study. Patients with the retracted tympanic membrane, thin tympanic membrane, tympanosclerosis fluid in the middle ear also excluded from the study after otoscopic examination. Hearing loss, defined as average pure tone threshold >26 dB for measurements pure tone average at frequencies of 0.5, 1.0, and 2.0 kHz. After exclusion and inclusion criteria, 200 patients with pure SNHL were evaluated. Hearing loss at speech frequency (500–2000 Hz) is seen in 17% of individuals. However, hearing loss present at 4000 Hz in 53.5% individuals (48% bilateral, 5.5% unilateral) and 8000 Hz in 63.5% individuals (61% bilateral, 2.5% unilateral) [Table 3].
Hearing loss also observed at 4000 Hz in 53.7% individuals. Mild degree hearing loss is present in 46% of patients, moderate hearing loss in 7% of patients, and moderately severe in 0.5% of patients. Hearing loss also observed at 8000 Hz in 63.7% individuals. Mild degree hearing loss is present in 50% of patients, moderate hearing loss in 13% of patients, and moderately severe in 0.5% of patients. Only 8000 Hz dip hearing loss in 10% of patients. Thus hearing loss was found in 122 (61%) members bilaterally. Unilateral hearing loss is present in 5 (2.5%) patients. Total hearing loss is present in 63.5% individuals (249 out of 400 ears). Twenty-one patients (42 ears) underwent a renal transplant, the average posttransplant duration was about 1 year, 11 patients (57%) among 21 have shown hearing loss. Severity of hearing loss in different frequencies is not the same. In summary, high frequencies are affected in 52%, middle frequencies in 9%, and low frequencies in 2.5% of individuals. About 2.5% had hearing loss in all frequencies. 10% of individuals have a hearing loss only at 8000 Hz. Patients were divided into three groups based on age (15–30, 31–45, 46–55 years) and two groups based on the duration of disease (<5, ≥5 years), hemodialysis in to two groups (<3 years, ≥3 years). All three variables compared with hearing loss. Hearing loss divided according into mild, moderate, moderately severe, severe, and profound and based on frequency into low, middle, and high frequency hearing loss. All patients had an SNHL. There is a significant correlation between duration of illness and hearing loss (P = 0.01) [Table 4].
Among all patients, 21 patients (42 ears) underwent a renal transplant, and posttransplant duration was about 1 year, 11 patients (57%) having hearing loss. No significant difference in hearing loss among transplant and nontransplant individuals. Tympanometry showed A curve in 92.5%, As curve in 2.5%, Ad curve in 5% on the right side and A curve in 89.5%, As curve in 6%, Ad curve in 6.5% on the left side. Reflexes are absent in 64.5%, present in 28.5% and elevated in 7% of individuals ipsilaterally and contralaterally in both ears. No, statistically significant correlation found tympanometry findings and duration of disease, hemodialysis, blood variables, and transplant status. There is no significant correlation between hearing loss between age, sex, duration of hemodialysis, blood urea, serum creatinine, transplant status, blood glucose levels, diastolic BP, hemoglobin levels, and tympanometry curve and reflexes (P > 0.05).
Hearing loss in the CKD population has been reported as being mainly sensorineural. Other causes of SNHL include age, diabetes, congenital hereditary otonephropathies, ototoxic drugs, such as furosemide or exposure to work- or industrial-related noise and stroke.
Participants with otosclerosis, conductive hearing loss on audiometry, congenital hearing loss, and diabetes mellitus were excluded from the study. Thus, CKD per se was associated with increased risk of an SNHL independent of other known confounding variables.
None of the participants in our study had the rare syndromes previously associated with hearing loss and renal disease.
There is a significant correlation between duration of disease and degree of hearing loss (P = 0.001). Mechanisms underlying the link between CKD and hearing loss are still unclear. It has been ascribed to uremic neuropathy and also to fluid and electrolyte abnormalities. Hearing loss among patients with CRF has been a common finding in studies investigating the effects of renal failure on auditory function. Despite differences in methodologies and indices of auditory function, the existence of hearing loss has been a common thread. The higher incidence of hearing loss among children with CRF has long been established and is constantly being verified by new studies. Patients with age >15 years excluded from the study to rule out syndromic hearing loss. Bergstrom et al. reported hearing the loss in 40% of the CRF patients on hemodialysis. Bergstrom and Thompson reported that 47% of 151 pediatric end-stage renal patients had hearing loss.
Hearing loss is a more common finding reported than vestibular dysfunction. Kusakari et al. reported on inner ear function of 229 patients on chronic hemodialysis. They found that 60% had hearing loss, 36% had vestibular dysfunction, and 26% had a combination of both.
Johnson and Mathog noted high frequency is hearing loss in 61 adults early in the course of hemodialysis. In our study, we had a high-frequency hearing loss in 50% of the patients and 13% hearing loss in patients with hemodialysis.
Charachon et al. reported that 75% of 54 patients with CRF had hearing loss. Zeigelboim et al. measured thresholds between 9 and 18 kHz in 37 patients with CRF undergoing conservative treatment and a control group with normal hearing function. Age ranges in both groups were 30–59 years. They found a more severe high-frequency hearing loss in the group with CRF. Hearing loss among patients with CRF seemed to deteriorate further a year after the first evaluation. Our study age range is 15–55 years. Hearing loss assessed up to 8 kHz only.
Bergstrom et al. compared a group of patients with hearing loss of unknown etiology, one with strial deposits and one with neither. They found no difference between the groups. Cochlear strial deposits were not related to vascular disease or calcium metabolism, but their size could be related to the presence of hearing loss. Histopathological studies of the inner ear in renal failure are sparse and provide valuable insight to how the disease may affect the association of hearing loss, disease duration, and blood tests.
An association between measures of renal and hearing function would specify how hearing is affected by CRF. Several studies have investigated correlations between duration of the disease, blood levels, and hearing.
Mancini et al. reported a hearing loss in 47.5% of patients with congenital disease and in 21% of children with acquired renal disease. Henrich et al. found that 75% of the patients showed no deterioration of hearing during the 4-year time of follow-up. They concluded that hearing loss is common in renal failure, but it does not worsen with duration of treatment. In our study, there is a significant correlation between duration of disease and the hearing loss.
Samir et al. found no correlation between pure tone audiometry findings and otoacoustic emission (OAE) measures and serum electrolyte levels. Kusakari et al. reported that inner ear dysfunction (including hearing loss and vestibular dysfunction or a combination) was not correlated with BUN and serum creatinine levels, or with and serum urea nitrogen, creatinine, potassium, sodium, calcium, and glucose levels. In our study, there is no correlation between age, sex, potassium, calcium, serum creatinine, diastolic BP, albumin, globulin level (P > 0.05).
In a similar report, Jorgenson et al. found that hearing loss was not related to changes in creatinine, potassium, sodium, calcium, glucose, BUN, BP, weight or hyperlipidemia.
Mancini et al. investigated SNHL in three groups of children with CRF: 14 on conservative treatment, 18 on hemodialysis, and 36 with renal transplants. They found SNHL in 29% of the children on conservative treatment, 28% of the children on hemodialysis, and 47% of the children with renal transplants. There were no correlations between hearing loss, duration of nephropathy, and hemodialysis treatment. In our study in adults, hemodialysis patient has 63.5% individuals having hearing loss, 57% of patients who underwent transplant had hearing loss.
Samir et al., found a significantly higher incidence of cochlear dysfunction among children on hemodialysis compared with children on conservative treatment, in contrast to despite overall similar median duration of hemodialysis. However, renal function among patients on dialysis is worse than among patients on conservative treatment, which further complicates the distinction between the effects of a more severe renal impairment from effects of the treatment., Albeit novel and interesting, this finding should be interpreted with caution, in light of the small number of subjects in the conservative treatment group. We did not have conservative treatment group to compare with hemodialysis.
The above studies showed that method of treatment may influence the impact of the disease on hearing, a topic yet to be conclusively investigated.
Early and more recent reports present conflicting findings concerning possible contributions of hemodialysis treatment to hearing loss in renal failure. Methodology of these investigations includes reports on the effects of a single session on hearing function and comparisons of patient groups with varying duration on the treatment. Ozen et al. reported an improvement of 20 dB in the hearing of patients following hemodialysis. They suggested that changes in serum osmolality, BUN, and fluid retention may reverse the hearing impairment postdialysis. However, as changes in the dialysis method alleviated wide fluctuations of these parameters, the hearing may not be as affected from hemodialysis today as it was at that time. There are several more recent reports in the literature contradicting the “hearing improvement” finding., Visenscio and Gerber reported that pure tone thresholds did not change significantly after hemodialysis. They did observe individual threshold shifts which they attributed to a temporary imbalance in the labyrinth caused by hemodialysis. Gartland et al. recorded pure tone thresholds on 31 patients before and after a session of hemodialysis. They included 125 Hz in the audiograms and documented a low frequency hearing loss, which improved significantly on one-third of the patients after dialysis. As low-frequency SNHL is related to endolymphatic hydrops, they postulated that changes in fluid balance during hemodialysis may be accountable for the low frequency hearing improvement. However, there was no correlation between weight and hearing changes after hemodialysis. In our study, we had a low incidence of hearing loss in lower frequencies. However, we did not include 125 Hz as in above study.
Ozturan and Lam found a notch at 6 kHz among CRF patients not related to hemodialysis indices. Therefore, the frequency specificity of possible CRF/hemodialysis effects on audiometry remains inconclusive. In our study, we had a notch at 8 kHz and 4 kHz. However, statistically not significant with hearing loss when compared to other indices. Serbetçioglu et al. tested pure tone thresholds of 19 patients 14–87 years of age prior to and 1 and 24 h following a randomly selected session of hemodialysis. They noted a permanent high-frequency hearing loss, but no specific effects of hemodialysis. Similarly, Nikolopoulos et al. found no effect of a single hemodialysis session on the hearing of nine hemodialyzed children. Kligerman et al. evaluated the hearing of patients with CRF, following 12 of them for 1 year as they were going through hemodialysis. The second group of patients not on hemodialysis were re-evaluated at the end of the year; a third group having received hemodialysis for 1.5, 2, 3, and 6 years were included in the study. In our study, we divided patients into two groups <5 and >5 years. There is no statistical significance when compared to hearing loss. Similarly, Bazzi et al. reported pure tone audiometric findings on three groups of patients: Patients on hemodialysis for <5 years, for 5–10 years and for more than 10 years. Both studies found a permanent high-frequency hearing loss in all groups related to the disease and treatment. They did not report a correlation between hemodialysis duration and severity of hearing loss. Therefore, duration on hemodialysis treatment did not appear to affect the degree of hearing loss in the CRF patient population. In our study, duration of hemodialysis had no significant correlation with loss. Ozturan and Lam examined the effects of a single session of hemodialysis on pure tone thresholds and distortion product OAEs (DPOAEs). They tested 15 patients of 19–45 years of age prior to and following a session of hemodialysis in a similar study with Stavroulaki et al. There were no significant changes in the pure tone thresholds or the DPOAE amplitude in either study. As ours cross-sectional study, we did not have follow-up study after hemodialysis. The literature concurs that the main site of lesion is cochlear with some retrocochlear findings in auditory brainstem audiometry. However, lack of correlation between hearing function and blood measures preclude a detailed description of the mechanisms causing hearing loss in CRF. Changes in the dialysis treatment have eliminated the temporary effects of a single session of dialysis on hearing function.
Bazzi et al. evaluated hearing loss in hemodialysis patients and concluded there is a high incidence of hearing loss in hemodialysis patients and that the number of years of dialysis treatment did not in itself influence the prevalence of hearing loss. Effects of both a single session of hemodialysis and long-term hemodialysis therapy have been studied in several other small studies. All patients in our study, all patients underwent hemodialysis. In our study, there is no significant correlation between hearing loss magnitude and duration of hemodialysis. All published studies to date have concluded that there is a high prevalence of hearing loss in this population and that dialysis treatment by itself does not alter hearing.
| Conclusion|| |
Evidence of a possible link between kidney function and hearing loss, as suggested by our study, potentially could modify the usual care of people with CKD.
It should encourage clinical nephrologists to include questions about hearing function in their preventive care protocols, to refer all patients reporting the hearing loss to a hearing health professional for evaluation and/or rehabilitation (e.g., hearing aids), and recommend that patients avoid further treatment with ototoxic medications to preserve their hearing ability.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Quick CA, Fish A, Brown C. The relationship between cochlea and kidney. Laryngoscope 1973;83:1469-82.
Irwin J. Basic anatomy and physiology of the ear. In: Newton VE, Vallely PJ, editors. Infection and Hearing Impairment. Ch. 1. Chichester, United kingdom: John Wiley and Sons, Ltd.; 2006. p. 8-13.
Alport AC. Hereditary familial congenital haemorrhagic nephritis. Br Med J 1927;1:504-6.
Furness DN, Hackney CM. Form and ultrastructure of the cochlea and its central connections. In: Scott-Brown's Otorhinolaryngology, Head and Neck Surgery. 7th
ed., Ch. 226. Great Britain: Michael Gleeson, Edward Arnold (Publishers) Ltd.; 2008. p. 3126-40.
Arnold W. Inner ear and renal diseases. Ann Otol Rhinol Laryngol Suppl 1984;112:119-24.
Davison AM, Cameron JS, Grünfeld JP, Kerr DN, Ritz E, Winearls CG. Oxford Textbook of Clinical Nephrology. 2nd
ed. Oxford, UK: Oxford University Press; 1998.
Dhingra PL, editor. Anatomy of ear. In: Diseases of Ear, Nose and Throat. 4th
ed., Ch. 1. New Delhi: Elsevier, Division of Reed Elsevier India Private Limited; 2007. p. 9.
Kusakari J, Kobayashi T, Rokugo M, Arakawa E, Ohyama K, Kawamoto K, et al.
The inner ear dysfunction in hemodialysis patients. Tohoku J Exp Med 1981;135:359-69.
Henrich WL, Thompson P, Bergstrom LV, Lum GM. Effect of dialysis on hearing acuity. Nephron 1977;18:348-51.
Bergstrom L, Jenkins P, Sando I, English G. Hearing loss in renal disease: Clinical and pathological studies. Ann Oto Rhino Laryngologica 1973;82 [Suppl]: 555-74.
Bergstrom L, Jenkins P, Sando I, English GM. Hearing loss in renal disease: Clinical and pathological studies. Ann Otol Rhinol Laryngol 1973;82:555-76.
Johnson DW, Mathog RH. Hearing function and chronic renal failure. Ann Otol Rhinol Laryngol 1976;85 (1 Pt 1):43-9.
Charachon R, Moreno-Ribes V, Cordonnier D. Deafness due to renal failure. Clinicopathological study (author's transl). Ann Otolaryngol Chir Cervicofac 1978;95:179-203.
Mancini ML, Dello Strologo L, Bianchi PM, Tieri L, Rizzoni G. Sensorineural hearing loss in patients reaching chronic renal failure in childhood. Pediatr Nephrol 1996;10:38-40.
Samir M, Riad H, Mahgoub M, Awad Z, Kamal N. Transient otoacoustic emissions in children with chronic renal failure. Clinical Otolaryngology Allied Sciences 1998;23:87-90.
Kusakari J, Kobayashi T, Rokugo M, Arakawa E, Ohyama K, Kawamoto K, et al
. The inner ear dysfunction in hemodialysis patients. Tohoku J Exp Med 1981;135:359-69.
Mancini ML, Dello Strologo L, Bianchi PM, Tieri L, Rizzoni G. Sensorineural hearing loss in patients reaching chronic renal failure in childhood. Pediatr Nephrol 1996;10:38-40.
Hutter JC, Kuehnert MJ, Wallis RR, Lucas AD, Sen S, Jarvis WR. Acute onset of decreased vision and hearing traced to hemodialysis treatment with aged dialyzers. JAMA 2000;283:2128-34.
Dhingra PL, editor. Hearing loss. In: Diseases of Ear, Nose and Throat. 5th
ed., Ch. 5. PL Dhingra: Elsevier, Division of Reed Elsevier India Private Limited; 2010. p. 43.
Pratt H, Brodsky G, Goldsher M, Ben-David Y, Harari R, Podoshin L, et al.
Auditory brain-stem evoked potentials in patients undergoing dialysis. Electroencephalogr Clin Neurophysiol 1986;63:18-24.
Magliulo G, Gagliardi M, Ralli G, Persichetti S, Muscatello M. BSER audiometry in haemodialysis patients. Clin Otolaryngol 1987;12:249-54.
Serbetçioglu MB, Erdogan S, Sifil A. Effects of a single session of hemodialysis on hearing abilities. Acta Otolaryngol 2001;121:836-8.
Nikolopoulos TP, Kandiloros DC, Segas JV, Nomicos PN, Ferekidis EA, Michelis KE, et al.
Auditory function in young patients with chronic renal failure. Clin Otolaryngol Allied Sci 1997;22:222-5.
Kligerman AB, Solangi KB, Ventry IM, Goodman AI, Weseley SA. Hearing impairment associated with chronic renal failure. Laryngoscope 1981;91:583-92.
Stavroulaki P, Nikolopoulos TP, Psarommatis I, Apostolopoulos N. Hearing evaluation with distortion-product otoacoustic emissions in young patients undergoing haemodialysis. Clin Otolaryngol Allied Sci 2001;26:235-42.
Bazzi C, Venturini C, Pagani C, Arrigo G, D'Amico G. Hearing loss in short and long-term haemodialyzed patients. Nephrol Dial Transpl 1995;10:1865-8.
[Table 1], [Table 2], [Table 3], [Table 4]