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Author: Dr Suneet Sood
Editor: Dr. Suneet Sood
Narrators: Thong Yi Kun, Alan Koay

Today we have an obstetrics case for discussion.

This 30-year-old woman had been seeing us in the antenatal clinic. She had three healthy babies, all delivered by caesarean section. This pregnancy had been uneventful. We admitted her at 37 weeks for an elective caesarean.

Why caesarean? Why not a trial of normal labour?

If a woman has had three previous caesareans it is virtually mandatory that future pregnancies should be delivered operatively. In these patients we do not recommend a trial of labour.

Okay.

At admission she was quite stable. She had mild abdominal pain and lower abdominal tenderness. She also complained of frequency of micturition.

Sounds like an infection!

Yes. The medical officer diagnosed urinary infection, and sent off the urine for microscopy and culture. He also started antibiotics.

Okay.

A few hours after admission, she developed a tachycardia. Uterine contractions were infrequent and irregular. Then the senior specialist came along. She saw the patient and said, this is impending uterine rupture.

Impending uterine rupture?

Yes. An immediate caesarean section was carried out. At surgery the senior specialist was proved right. The patient had marked thinning of the uterine scar, and in a few hours the uterus would have ruptured, with loss of the baby and a serious threat to the mother’s life. As it turned out, the patient had an unremarkable postoperative course.

That was a smart diagnosis by the specialist!

In actual fact, the medical officer’s mistake is bigger. Any patient who has had a previous caesarean section is at risk of uterine rupture through the previous scar. The urinary features and the abdominal tenderness should have alerted the medical officer.

Why does impending uterine scar rupture cause urinary symptoms?

There are three reasons why impending scar rupture causes urinary symptoms.

First cause: the operated uterus often becomes adherent to the bladder anteriorly. When the uterus stretches too much, this stretch involves the bladder, with the development of frequency.

Okay, adhesions between uterus and bladder cause frequency. Second cause?

Secondly, abnormal stretching of the uterine scar causes local inflammation. Inflammatory peptides diffuse through to the bladder, causing a mild cystitis. That causes frequency.

Okay, scar stretching causes inflammation, which cases adjacent cystitis. Third cause?

Thirdly, the afferents of the lower urinary tract travel along two regions: T11 to L2, and S2 to S4.1 Afferents from the uterus also travel up T11- L1. You can see that there is considerable overlap. In this setting sensation from the uterus may easily be referred to the bladder. [SLOW]

Oh, so the cause of the frequency is a sensation from the uterus referred to the bladder, causing a sort of spurious frequency?

Yes.

Nice! Thank you. So, the bottom line is: sensations from the uterus can be referred to the urinary bladder causing a desire to pass urine. Doctors should remember that in a patient with previous caesarean, frequency of micturition may be a sign of impending scar rupture.

References:
de Groat WC, Yoshimura N. Afferent nerve regulation of bladder function in health and disease. Handb Exp Pharmacol. 2009;(194):91-138.