Urinary Retention in Older Adults with Hyponatraemia admitted to Internal Medical and acute Geriatric wards

doi:10.21203/rs.3.rs-4896469/v1

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Urinary Retention in Older Adults with Hyponatraemia admitted to Internal Medical and acute Geriatric wards

https://doi.org/10.21203/rs.3.rs-4896469/v1

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Background

Hyponatraemia and urinary retention are common medical problems. Whilst associations between the two are documented, research has not clearly highlighted the prevalence of urinary retention in hyponatraemic patients.

Objectives

Determining the prevalence of urinary retention in hyponatraemic patients and assessing whether urinary catheter insertion itself affects the correction rate.

Methods

A prospective, single centre, observational study including patients hospitalised in internal medicine and geriatric wards. A total of 199 patients were investigated: 100 with hyponatraemia ≤129 mEq/L, of these, 70 had severe hyponatraemia ≤125 mEq/L and 99 normonatraemic controls. The incidence of urinary retention was checked in all groups. Hyponatraemic patients underwent complete assessment for the cause of hyponatraemia and sodium levels were followed up for 48 hours.

Results:

There was a marked increase in the incidence of urinary retention in hyponatremic patients as compared to those with normal sodium levels (41% vs 21% p=0.004). When comparing to those with severe hyponatraemia, a slightly greater difference was found (44% vs 21% p=0.001). When comparing the hyponatraemic patients with and without urinary retention, there was no difference in sodium correction rate between the two groups. Patients with polyuria secondary to post obstructive diuresis had a more rapid sodium correction (9.2±6.8mEq/L vs 5.8±4.8mEq/L (p=0.05))

Conclusions:

There is a significantly higher prevalence of urinary retention in patients with hyponatremia which is associated with the severity of hyponatraemia. Post obstructive diuresis following catheter insertion is a predictor of rapid sodium correction. We recommend a routine bladder scan for all patients with hyponatraemia.

Hyponatraemia

urinary retention

older adults

There is a significantly higher prevalence of urinary retention in patients with hyponatremia which is associated with the severity of hyponatraemia.
Post obstructive diuresis following catheter insertion is a predictor of rapid sodium correction.
We recommend a routine bladder scan for all patients with hyponatraemia.

Hyponatraemia and urinary retention are common in acute medical and geriatric wards. Several studies have shown an association between these [1, 2, 3, 4] but none have evaluated the prevalence of urinary retention in patients with hyponatraemia.

In a prospective controlled study [5] the reverse association was evaluated, analysing the incidence of hyponatremia in patients with acute urinary tract obstruction (aUTO). The incidence of hyponatraemia was similar in patients with aUTO compared with the control group, independent of age, baseline co-morbidities or cause of admission. However, the mean sodium level was lower, and the incidence of severe hyponatraemia was significantly higher, in patients with aUTO as compared with controls. Notably, relief of aUTO led to a significant and rapid improvement in serum sodium level.

Similarly, a previous case series on a geriatric ward described six older patients with co-existing hyponatraemia and urinary retention. In all these patients, serum sodium levels normalised and remained stable following foley catheter insertion and water restriction. Most of the patients underwent extensive diagnostic workups during their hospitalisation and no specific cause of hyponatraemia other than urinary retention was found [4]. Other anecdotal reports which are summarised in two recent studies have highlighted hyponatraemia in patients with (aUTO), which subsides rapidly with relief of the obstruction [1, 5].

The primary aim of this study was to determine the prevalence of urinary retention in patients with hyponatremia; we compared the prevalence of urinary retention in patients with severe (< 126 mEq/L) and moderate (126–129 mEq/L) hyponatremia to patients with normal sodium levels.

The secondary aim was to assess whether urinary catheter insertion itself affected the correction rate.

A prospective, observational, single-centre, study conducted in Shaare Zedek Medical Center (SZMC), Jerusalem, Israel, a university-affiliated 1,000-bed general community hospital. During the study period, general medical patients aged 65 years and older who had a serum sodium level of 129 mEq/L or less were investigated. Patients with haemodialysis, nephrostomy, ileal conduit or permanent catheter were excluded.

A bladder scan was performed on all patients. Those with urinary retention (defined as residual volume > 400 ml) had a urinary catheter inserted. Demographic and clinical characteristics including clinical presentation and drug history were collected. All patients underwent a complete physical examination and an assessment of their volaemic status. The laboratory work up included a complete blood count, biochemistry with serum osmolarity, urinary sodium and osmolarity. Thyroid-stimulating hormone (TSH) levels were obtained in most patients and cortisol levels taken where there was clinical suspicion of adrenal insufficiency. Most patients underwent a chest X-ray. Other radiological tests were performed as considered necessary by the attending physician. Syndrome of inappropriate ADH secretion (SIADH) was defined clinically [6]. Sodium level was repeated during the following 48 hours.

We collected a control group of hospitalised 65 years and older patients in internal medical and geriatric wards with normal sodium levels to evaluate the incidence of urinary retention in normonatraemic hospitalised patients.

The study was approved by the Ethics Committee of SZMC. Written consent was not obtained from individual patients, as the study was based on data collected for routine care.

One hundred and ninety-nine patients were investigated. One hundred with hyponatraemia less than 129 mEq/L, of these, 70 patients had severe hyponatraemia ≤ 125 mEq/L. There were 99 normonatraemic controls.

There was a marked increase in the incidence of urinary retention in hyponatremic patients as compared to those with normal sodium levels (41% vs 21% p = 0.004). In the 70 patients with severe hyponatraemia the incidence of urinary retention was even higher 44% (p = 0.004). There was no significant difference in sex or age of the patients between the study and control group as can be seen in Table 1. We note the slightly lower prevalence of men in the hyponatraemia group (33% Vs 45%) and despite this, the higher prevalence of urinary retention.

In the 41 patients with hyponatraemia and urinary retention, the retention volume was 715 ± 367ml which was similar to the volume in 21 patients with urinary retention in the normonatraemic group 670 ± 246ml (p = 0.61). There was no correlation between retention volume and sodium level (r=-0.063, p = 0.63).

Table 2 compares hyponatraemic patients with and without urinary retention. These sub-groups were similar in age, gender, and co-morbidity burden. Similarly, there was no difference in use of drugs commonly causing hyponatraemia, volume status or blood test results. Mean basal sodium levels were similar in both groups 123 mEq/L vs 121 mEq/L (p = 0.178). Of the 41 patients with hyponatraemia and urinary retention, 19 (46.3%) had SIADH.

Of note, there was a very small group of six patients who did not receive any specific treatment for hyponatraemia. Four of these had urinary retention which was relieved with a catheter. The mean sodium improvement in the four patients with urinary retention was 10.8 ± 6.1 mEq/L, much above the overall average of 6.4 ± 5.4 mEq/L (p = 0.17).

Regarding factors associated with correction of sodium levels, other interesting data emerged from our study group regarding volume status and polyuria.

The volume status of patients had a minor effect on the rate of correction: Hypervolaemic patients had a slightly slower correction rate than euvolaemic and hypovolemic patients (hypervolemic 4.3 ± 3.1 mEq/L, euvolemic 7.1 ± 6.0 mEq/L, hypovolemic 7.2 ± 5.5 mEq/L (p = 0.022)).

Patients with polyuria secondary to post obstructive diuresis did have more rapid sodium correction; 11 patients with polyuria had a sodium correction rate of 9.2 ± 6.8 mEq/L compared to 24 patients without polyuria who had a correction rate of 5.8 ± 4.8 mEq/L (p = 0.05).

Hyponatremia is a common medical problem and whilst previous research has shown an association with urinary retention, the prevalence of urinary retention in patients with hyponatremia has not been described. This prevalence is important clinical information when evaluating a patient with hyponatremia. Indeed, we found a significantly raised prevalence of urinary retention amongst patients with hyponatremia.

Interestingly, our control group of similar hospitalised patients had a markedly high prevalence of urinary retention of 21%. This high prevalence amongst unwell, bed restricted inpatients is worthy of investigation in future research.

Regarding our secondary aim of whether catheter insertion itself corrects hyponatraemia, our previous study [5] showed that in a small group of seven severely hyponatraemic patients, urinary catheter insertion led to a significantly increased sodium correction rate (9.6 ± 3mEq/L/48hours). Our current study did not demonstrate this difference. Notably, in patients with polyuria after catheter insertion, there was a significant sodium increase. Thus, polyuria could have been the cause of the improvement seen in the above study [5]. Consistent with this finding, a recent case series of three patients with severe hyponatraemia and urinary retention all had polyuria and a rapid sodium correction due to free water clearance and interventions were necessary to prevent the rapid increase of plasma sodium [1].

In our study, we could not isolate catheter insertion as an independent factor for correcting sodium level because everyone received standard hyponatremia treatment together with catheter insertion when needed. However, in a very small group of four patients for whom the only treatment was catheter insertion, the sodium correction was above average (10.8 mEq/L). This may be an important observation because these patients improved at an above average rate despite receiving no other treatment. Future research would investigate catheter insertion as the sole treatment for asymptomatic patients with hyponatraemia and urinary retention.

Concerning the main finding of increased prevalence of urinary retention in patients with hyponatraemia, we summarise several theories to explain the pathophysiology:

Hyponatremia in urinary retention could result from ADH secretion secondary to the pain of bladder distension in aUTO. Indeed, the prevalence of patients with SIADH in this group is 19 of the 41 (46%). There was no correlation between the volume of retention in patients with urinary retention to sodium level.

An alternative explanation may be “functional aUTO” where the hyponatraemia causes an altered conscious state in which the patient refrains from passing urine and thus develops urinary retention. Similarly, hypervolaemic hyponatraemic patients receiving diuretic therapy may find that the large urine volume and frequency make it impossible to mobilise to the lavatory and thus withhold urine output.

Additionally, patients experiencing decreased urinary output may drink more believing it will encourage urination and dilutional hyponatraemia. This itself may exacerbate hyponatraemia, as the therapeutic response would be to restrict water [3].

Further research to investigate the causes of urinary retention in hyponatraemia should be conducted. For example, the ADH theory could be tested by checking ADH levels in patients with different retention volumes.

This study was impressive for its large number of patients in the study and control groups. There was detailed clinical and laboratory data available for most patients in the study group. However, this was a descriptive study which did not allow for assessing the effect of interventions (for example assessing catheter insertion as a sole treatment) in a significant way.

In summary, there is a significantly higher prevalence of urinary retention in patients with hyponatremia which is associated with the severity of hyponatraemia. We recommend a routine bladder scan for all patients presenting with hyponatraemia. A significant predictor of rapid sodium correction is polyuria following urinary catheter insertion.

On behalf of all authors, the corresponding author states that there is no conflict of interest.

Table 1

The characteristics of patients according to sodium level
	Na < 126 mEq/L (n = 70)	Na126-129 mEq/L (n = 30)	Na < 130 mEq/L (n = 100)	Na ≥ 135 mEq/L (n = 99)	P value*
Age (year), M (SD)	84.4 (8.5)	84.9 (7.9)	84.6 (8.3)	84 (8.4)	.618
Sex (male) (%)	25 (36)	8 (27)	33 (33)	45(45)	.098
Na (mEq/L), M (SD)	119.8 (4.4)	127.1 (1.2)	122 (5.1)	139.1 (2.7)	< 0.0005
Urinary retention (%),(mean volume ml)	31 (44) (705)	10 (33) (749)	41 (41) (715)	21 (21) (670)	.004
* Between research group (Na < 130) and compare group (Na ≥ 135 mEq/L)

Table 2

–Hyponatraemic patients with and without urinary retention
Urinary retention	Yes (n = 41)	No (n = 59)	P value
Age(year), M (SD)	84.5 (8.5)	84.7 (8.2)	.900
Sex, (male, N (%))	14 (34)	19 (32)	1.000
Comorbidities, N (%)
Diabetes mellitus	13 (32)	18 (31)	1.000
Hypertension	30 (73)	46 (78)	.753
Congestive heart failure	11 (27)	19 (32)	.723
Cerebrovascular accident	4 (10)	9 (15)	.616
Chronic kidney disease	9 (22)	12 (20)	1.000
Malignancy	4 (10)	9 (15)	.616
Hospitalization reason, N (%)			.945
Hyponatremia	8 (20)	14 (24)
Fall	5 (12)	7 (12)
Cardiovascular disease	6 (15)	11 (19)
Infection	11 (27)	14 (24)
Other	11 (27)	13 (22)
Medication, N (%)
Thiazide	2 (5)	4 (7)	1.000
SSRI	5 (12)	5 (9)	.786
Opioids	1 (2)	4 (7)	.608
Volaemic status, N (%)			.215
Euvolaemic	21 (51)	25 (42)
Hypervolaemic	12 (29)	13 (22)
Hypovolaemic	8 (20)	21 (36)
Admission Na (mEq/L), Mean (SD)	121 (5.56)	123 (4.95)	.178
Admission NA ≤ 125, N(%)	30 (73)	36 (61)	.295
NA delta (mEq/L) (48 hours), M (SD)	6.8 (5.4)	6.1 (5.4)	.518
Volume retention (ml), M (SD)	715(367)	151(116)	< 0.005
Laboratory, M (SD)
Bun (mg/dL)	30.7 (22.9)	30.7 (24)	.994
Creatinine (mg/dL)	1.4 (1.4)	1.3 (1.2)	.762
Albumin (gr/dL)	3.3 (0.5)	3.2 (0.7)	.105
Potassium (mEq/L)	4.2 (0.8)	4.3 (0.7)	.549
Hemoglobin (g/dL)	11.3 (1.8)	10.9 (2.1)	.358
WBC (10ᶺ3/uL)	11.2 (4.6)	11.8 (14.8)	.820
Platelets (10ᶺ3/uL)	288.5 (99.8)	232.5 (89.7)	.004
TSH (mIU/L)	3.1 (4.5)	2.99 (3.5)	.952
Exitus, N (%)	2 (5)	8 (14)	.278
Treatment, N (%)
Saline 3%	13 (32)	18 (31)	1.000
Water restriction	7 (17)	14 (24)	.580
Furosemide	13 (32)	20 (34)	.990
Drug withdrawal	9 (22)	14 (24)	1.000
NaCl 0.9%	30 (73)	41 (70)	.861

van der Bilt F, Alsma J (2023) Hyponatraemia caused by transient syndrome of inappropriate antidiuresis to urinary retention. Intern Med J 53:285–288
Moskowitz DW (1992) Functional obstructive uropathy: a significant factor in the hyponatremia of psychogenic polydipsia? J Urol 147:1611–1613
Pyle R, Scott M, Bartholomew J et al (2011) Accidental polydipsia and hyponatremia from diphenhydramine urinary retention. Am J Med 124:e5–6
Galperin I, Friedmann R, Feldman H et al (2007) Urinary retention: a cause of hyponatremia? Gerontology 53:121–124
Shapiro DS, Alexandrovich I, Sonnenblick M et al (2022) Prospective determination of the incidence and severity of hyponatraemia in older hospitalised patients with acute urinary tract obstruction. Age Ageing 51. 10.1093/ageing/afab234
Syndrome of inappropriate antidiuretic hormone - Symptoms, diagnosis and treatment | BMJ Best Practice US

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You are reading this latest preprint version

Urinary Retention in Older Adults with Hyponatraemia admitted to Internal Medical and acute Geriatric wards

Status:

Version 1

Abstract

Key Points

Introduction

Methods

Results

Discussion

References

Status:

Version 1