When do I actually need a PVR scan?

When Do I Actually Need a PVR Scan? The Real-World Guide for Private Practice Physios

By the team at Pelvic Physio Mentor

Picture this: You're six months into your pelvic health journey, sitting across from a patient who's describing urinary urgency and frequency. You're thinking about bladder retraining, but then that little voice in your head asks: "Should I be checking if she's emptying properly first?"

If you don't have an ultrasound unit in your clinic (and let's be honest, many of you won't), this question becomes even trickier. Do you send everyone out for a post-void residual scan just to be safe? Or can you make confident treatment decisions without one?

This week, one of our mentees asked exactly this question: "I don't have an ultrasound unit - should I be sending every patient out to medical imaging for a PVR before starting bladder retraining?"

My answer? Not necessarily. Let me explain why.

The High-Risk Groups: When PVR Should Be on Your Radar

There are definitely some patient groups where I'm automatically thinking about post-void residuals. These are the ones where retention is common enough that you'd want to rule it out:

Early postpartum women with any voiding issues:

  • Difficulty getting their stream started

  • That nagging feeling they're not quite empty

  • Sudden leaks when they stand up or move (could be overflow)

  • Any urinary incontinence in those first few weeks

Post-surgical patients:

  • Anyone who's had recent pelvic surgery, especially if they had a catheter

  • Even "minor" procedures can temporarily affect voiding

  • The combination of anesthesia, pain meds, and surgical trauma is a perfect storm for retention

Pessary fittings:

  • Although you might not be doing these (file this away for later) - before you send someone home with a pessary, you must know they can empty around it

  • Even a well-fitted pessary can interfere with complete emptying

Anyone you're considering for bladder retraining:

  • This is where it gets interesting, and where my mentee's question came from

The Bladder Retraining Dilemma

Here's the thing about bladder retraining - if someone has significant retention and you start teaching them to hold on longer, you could potentially make things worse. So the question becomes: do you need a PVR on everyone before starting urge suppression techniques?

The answer depends on what you're seeing clinically.

When You Can Probably Skip the External Referral

If your patient has a straightforward overactive bladder presentation - clear urge episodes (wet or dry), some reasonable voiding volumes on their bladder diary (200-400ml typically), no complaints about emptying, normal stream - then you're probably fine to start conservative treatment and monitor how they respond.

I'm comfortable proceeding without a PVR if:

  • Their bladder diary shows good voiding volumes

  • They have reliable urge sensations

  • No history of recurrent UTIs

  • They report feeling completely empty after voiding

  • Stream quality sounds normal when they describe it

Medical Emergency Alert: When PVR Becomes Urgent

Before we dive into the subtle signs, let's talk about the situations that need immediate medical attention - not a referral for next week, but urgent assessment today.

Overt retention red flags:

  • Patient reports they feel like they need to urinate but can't get anything out

  • Severe lower abdominal pain with urinary urgency

  • Palpable bladder (you can feel it as a firm mass above the pubic bone)

  • Extreme patient distress about inability to void

High-level PVR emergency: If you do get a PVR result and it's >400-500ml, that's not a "monitor and see" situation - that needs same-day medical review. At these volumes, we're talking about potential kidney complications and the need for catheter drainage.

These situations bypass all the decision-making we're about to discuss. When you see overt retention or really high PVR, you're referring to ED or arranging urgent GP review, not booking them in for bladder retraining next week.

When Your Senses Should Be Tingling

There may be not the clear cut emergency scenarios discussed above but are definitely flags that make me think "hang on, something's not quite right here with their emptying." These are the signs of what we call "covert retention" - where patients might be voiding, but you suspect they're not completely emptying:

The suspicious symptoms:

  • Frequent voiding but consistently small volumes (under 150ml on diary)

  • They describe their stream as weak or taking ages to get started

  • Multiple UTIs without an obvious cause

  • That post-void dribble that's really bothering them

  • They mention having to strain or push to get their urine out

  • Sudden unexpected leaks, especially when standing up from sitting

  • They just don't feel "right" about their emptying, even if they can't describe it clearly

The patterns that don't add up:

  • Overactive bladder symptoms but voiding tiny amounts frequently

  • Mixed incontinence where the stress component might actually be overflow

  • Prolapse symptoms combined with voiding concerns

The "Is It Worth the Hassle?" Decision

Let's be honest - referring someone out for a suspected small range PVR when you don't have your own equipment is a bit of a hassle. They need to:

  • Get a referral (sometimes through their GP first)

  • Book an appointment at medical imaging

  • Remember to arrive with a full bladder

  • Pay for the scan (if not bulk-billed)

  • Wait for results to come back to you

So if you're clinically confident that retention isn't an issue, and their presentation fits a straightforward overactive bladder pattern, it's reasonable to start treatment and monitor closely.

Where to Send Them When You Do Need a PVR

When you've decided the scan is worth it, you have a few options:

Medical imaging centers:

  • Usually the fastest option

  • May accept direct physio referrals (check locally)

  • Often not bulk-billed, so there's a cost to patients

GP with ultrasound capabilities:

  • Many modern GP practices have basic ultrasound

  • Usually bulk-billed

  • Might take longer to get an appointment

Hospital outpatient departments:

  • Continence clinics often have scanning but may have prohibitively long waiting lists

  • Usually bulk-billed

  • IF you detect a NEW presentation in your clinic of suspected significant PVR then sent straight back to ED with a letter (typically you might see this in early post partum) as discussed above!

The referral letter trick: Be specific. Write "Request for post-void residual measurement" rather than "bladder assessment." You'll get what you need faster.

My Clinical Decision-Making Process

Here's honestly how I think about it:
Overt retention or high vol retention =Straight to ED/GP

High suspicion of covert retention + treatment won't work if they're retaining = Send for PVR first

Low suspicion + straightforward presentation = Start treatment, monitor closely

Any doubt or red flags = Better safe than sorry, get the scan

If someone doesn't improve with bladder retraining as expected, or if new symptoms develop, that's when I'd definitely want that PVR even if I didn't think I needed it initially.

The Monitoring Approach

When you decide to proceed without a PVR, you need to be extra vigilant about monitoring. I'm looking for:

  • Are their symptoms improving as expected?

  • Any new concerns about emptying?

  • Developing any signs of UTI?

  • Voiding patterns changing on their diary?

If things aren't tracking as they should, that PVR moves up the priority list pretty quickly.

Trust Your Clinical Judgment

The reality is, you don't need a PVR on every single patient before starting conservative bladder management. Good clinical assessment, detailed history-taking, and careful monitoring can often tell you what you need to know.

But when you have that gut feeling that something's not quite right with their voiding, trust it. The "hassle" of an external referral is worth it for patient safety and treatment success.

Remember, we're not trying to be perfect diagnosticians - we're trying to be safe, effective practitioners who know when we need more information to make good treatment decisions.

The Bottom Line

Not every patient needs a PVR before bladder retraining. But the patients who do need one really, really need one. Learning to distinguish between these groups is part of developing your clinical reasoning in pelvic health.

When in doubt, err on the side of caution. But don't let the lack of in-house equipment stop you from providing excellent care. Good assessment skills and knowing when to seek additional information are just as valuable as having all the technology at your fingertips.

Struggling with clinical decision-making around bladder assessment? Our mentoring program helps practitioners develop confidence in knowing when investigations add real value versus when you can proceed with treatment. Learn more about building your clinical reasoning skills with support from experienced pelvic health practitioners.

Karina Coffey