**Abstract**

Emerging evidence has shown that long-term and chronic ketamine use or abuse can lead to damages in the urinary tract, a spectrum of clinical presentations from mild irritative lower tract symptoms to painful gross haematuria and renal damages. First reported by a Hong Kong group of urologists in 2007, the phenomenon has since then been identified worldwide. Most of the ketamine abusers were adolescents and young adults, and the symptomatology resembled those of chemical cystitis or interstitial cystitis. Endoscopic features of ulcerative cystitis, radiological features of thickened and contracted bladder wall with or without obstruction to upper urinary tract, and histopathological features of inflammation and fibrosis and urothelial metaplasia changes were described. With increasing clinical experience in managing this group of patients, clinical pathways and medical and surgical treatment options have been developed. Animal studies on the effects of ketamine exposure on the urinary system have also been conducted to help us understand the underlying pathophysiology for this distinct entity.

**Keywords:** ketamine, cystitis, hydronephrosis, detrusor overactivity, uropathy

#### **1. Introduction**

Ketamine is listed in the WHO Essential Medicines List since 1985 as an anaesthetic and analgesic. Unlike other commonly used anaesthetic agents, ketamine does not tend to cause respiratory depression or hypotension, making it ideal for use as a general sedative and in veterinary medicine [1].

However, ketamine is also a drug of abuse. The United Nation's World Drug Report 2019 shows that ketamine has been the dominant hallucinogenic seized by authorities globally, accounting for 87% of such seizures in the past 5 years [2]. In 2017, the global quantity of ketamine seized was approximately 11,000 kilogrammes, the majority of which was in Asia [3]. Most ketamine seized, in the order of descending quantity, was reported by mainland China, followed by Taiwan, Hong Kong, Malaysia, Myanmar, Thailand, the United Kingdom, India, and the Netherlands [3]. In Taiwan, ketamine has been the most frequently abused illicit drug since 2006. The volume of seizures there grew from 916 kg in 2009 to 1187 in 2010 [4]. However, ketamine is becoming more and more popular not only in Southeast Asia but in Europe as well. The number of ketamine users in the United Kingdom grew from 85,000 in 2006 to 113,000 in 2008, becoming the fourth most popular illicit drug among UK clubbers [5]. Its popularity could be explained by its low market price among recreational drugs and also the difficulty in cracking down on its trafficking, as it is produced legally for medical use [6].

The chronic and illicit use of ketamine is associated with urinary tract damages. Structural damage to the bladder, ureters, and kidneys has been demonstrated in numerous animal and human studies. Patients usually present to the urological service with symptoms such as urinary frequency, haematuria, and dysuria. Management is multidisciplinary, as a big part of treatment success lies not only in urological interventions but also in successful abstinence.
