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Ambulatory UDS: How & when?

Dr Vikas Panwar

AIIMS, Rishikesh

Urodynamic Study directly assesses the patient’s lower urinary tract symptoms by reproducing the patient’s symptoms. Due to physiological and technical aspects, many patients fail to reproduce symptoms in conventional urodynamic studies. Ambulatory urodynamics (AUDS) is helpful in such a setting where the patient can do their normal activities.

Technique: Before the test is started it is mandatory to ensure that the patient understands and is able to follow some important instructions. Air Charged catheters are inserted into the bladder and the anal canal. Sufficient catheter length should be inserted into the bladder/rectum and the catheters must be securely taped adjacent to the anus and external urethral meatus to reduce the risk of catheters falling out as well as to reduce movement artifacts. The patient can then dress and the catheters can be connected to the AUDS recording system. AUDS catheters are calibrated and recording is started. Patient needs to record various events like drinking, walking, first sensation, first desire, normal desire, strong desire, urgency and finally voiding and then graph is interpreted.

Ambulatory UDS is based on diuresis-induced natural bladder filling in contrast to conventional UDS in which artificial filling is used. Therefore, it overcomes many shortcomings of conventional UDS, such as the inadequate representation of the natural filling of the bladder. Ambulatory UDS is useful in representing the symptoms in a near-normal situation. AUDS helps in detection of underlying pathophysiology of urinary incontinence in significantly more number of patients and improved detection of Detrusor overactivity compared to conventional UDS. AUDS makes patient ambulate normally and avoids being positioned in prolong sitting position and thus leads to less anxiety among patients and thus is more acceptable to patients especially females. Although AUDS has few shortcomings like prolong duration of study, difficulty in interpretation of graph, long learning curve, availability and cost related issues. According to current ICS recommendations, AUDS is recommended as a second line test, especially when a conventional urodynamic investigation has failed to produce or explain patient’s symptoms. Poor patient mobility, cognitive impairment or inabilities to follow instructions are relative contraindications for AUDS.

AUDS is gaining popularity in terms of being more representative of patient’s symptoms and being more acceptable to patients although still scientific evidence regarding its utility is limited.

LUNA recording system

Figure 4: LUNA recording system

Ambulatory UDS graph

Figure 5: Ambulatory UDS graph

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