3kg baby replaced by 3kg of urine

Urine replaces baby
3.2 L of urine replaces 3.2kg of baby. 

I’m going to have a withdrawal bleed once I leave O&G’s hormonal fuelled adventures behind. It has been a mix of the high (on entanox) and the low (lying placenta). I’m no longer scared of the concept of pregnancy (even if the BNF seems to be – “no evidence of harm but what the hell – manufacturers advise avoid”). I’m glad I did it, but I’m more glad it’s over.

That said, it just wouldn’t be O&G without one last not-normal-fluid-out-an-orifice scenario to work through. Towards the end of the placement, I noticed several women who had normal vaginal deliveries developed urinary retention. Post op C section retention is nothing new; pretty much any major surgery has this risk. However, I was unaware of how frequent retention is post vaginal delivery, and how best to recognise/manage it.

Before we dive in, there’s a little analogy I find helpful. I used to think urinary retention must be absolute i.e. if the patient is passing something, it can’t be retention. I now think of it more like faecal impaction than full-on bowel obstruction. Just like you can have some overflow with faecal impaction, you can pass little overflow-y voids with retention. If the voiding volume is small and/or there’s voiding difficulty and/or suprapubic pain and/or there’s a high residual, treat it as potential retention even if there is some urine output.

A woman has a normal delivery. There was a second degree tear which was sututred. She had difficulty passing urine post delivery, passing 50ml then 60 ml in 6 hours post delivery. She complains of lower abdominal pain. She is a little tachycardic. The team assume she is dry and give her 3.5L orally over the next 24 hours. The urine output does not pick up, and her observations remain the same.

Our super SHO (not me) does a thorough examination discovers that there is suprapubic tenderness combined with the urge to pass urine. The patient feels really uncomfortable. A urinary catheter is passed. It drains 3.2L.

How did this happen?

During pregnancy (especially the third trimester), the bladder tone decreases and bladder capacity enlarges. Before she gives birth, the pressure of the gravid uterus compressing the bladder helps maintain voiding pressure. After delivery, the bladder expands and intravesical pressure drops. In 1.7-17.9% of women who have a vaginal delivery, this leads to retention.

So it’s kinda normal then. When do I worry about it? 

It can take up to 6 hours after a normal delivery for bladder sensation to return to normal (more if an epidural was used). If a woman has not passed urine within 4 hours after delivery despite adequate fluid intake, she should be given every opportunity to pass urine naturally. This means controlling pain, keeping her mobile, giving her privacy and perhaps trying a warm bath. If it reaches 6 hours, it’s time to catheterise.

But this woman passed a little. Does that count?

One void less than 200ml could still be consistent with retention (especially if accompanied with voiding symptoms such as suprapubic pain, poor stream, leaking/passing urine without the urge etc.)

OK, so now that we catheterised her, she had a residual of 3.2L. How you gonna deal with that?

There is no formal guideline. A ‘normal’ adult bladder distends up to 400-600ml. Distension beyond this volume should be uncomfortable. The fact it drained 3.2L means her bladder has been significantly distended.

That said, immediately post partum the bladder is naturally a little distended.

The urge to pass urine starts at around 150-250ml. If there’s a post-void residual of more than 150ml, it suggests a voiding issue.

You didn’t answer my question.

Fine. I found several approaches used by different midwife units. Nottingham’s guidelines specifically talk about how variable the guidelines from various units are. One approach for symptomatic retention that I found intuitive was from a New Zealand. With some slight modification to fit in with what I generally saw being done in the UK, we’ve got the following plan for overt (i.e. symptomatic) retention:

Once the 6 hour deadline has elapsed, you re-catheterise the patient. If there’s a small residual (<150ml) it’s fine – it’s not retention (maybe she was a bit dry). If it’s medium (150-700ml) keep it in for 24 hours and repeat the TWOC then. If it’s big (past 700ml), keep it in for 48 hours. This gives more time for the bladder to be unfull and hence hopefully return to its normal size.

On the second TWOC, if she does a good void (>200ml) within 6 hours, you check the residual. If the residual is less than 150ml, it’s all good. If it’s bigger, or she doesn’t do a good void in the new 6 hour deadline, then she failed the second TWOC which usually means a 7 day in dwelling catheter before a re TWOC. Another approach is intermittent self catheterisation.

If the volume for the first TWOC is bloody ridiculous like 3.2L, go straight for re-TWOC in 7 days.

Covert retention (post voiding residual >150ml without symptoms) is nicely covered by the same New Zealand guidelines. It seemed similar to what I see in the UK.

How is it going to resolve?

Postpartum retention is usually a short-term problem that resolves over weeks. It can lead to a persistent hypotonic bladder if poorly managed.

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