1/🧵
Why does catamenial pneumothorax (pneumothorax that recurs with menstruation) almost always occur on the right side?
Why doesn't it affect both sides of the chest equally?
#medtwitter #tweetorial
Why does catamenial pneumothorax (pneumothorax that recurs with menstruation) almost always occur on the right side?
Why doesn't it affect both sides of the chest equally?
#medtwitter #tweetorial
2/
Catamenial pneumothorax was first described in 1958.
A woman presented w/ 12 episodes of right-sided pneumothorax over 1 year, recurring monthly w/ menstruation.
Thoracotomy revealed thoracic endometriosis.
pubmed.ncbi.nlm.nih.gov/13598643/
Catamenial pneumothorax was first described in 1958.
A woman presented w/ 12 episodes of right-sided pneumothorax over 1 year, recurring monthly w/ menstruation.
Thoracotomy revealed thoracic endometriosis.
pubmed.ncbi.nlm.nih.gov/13598643/
3/
Endometriosis = extra-uterine implantation of endometrial tissue
Mechanisms include:
💡Retrograde menstruation ➡️ abdominopelvic spread
💡Blood/lymph-borne deposition
💡Metaplasia
🔑Retrograde menstruation is considered the predominant mechanism.
ncbi.nlm.nih.gov/pmc/articles/P…
Endometriosis = extra-uterine implantation of endometrial tissue
Mechanisms include:
💡Retrograde menstruation ➡️ abdominopelvic spread
💡Blood/lymph-borne deposition
💡Metaplasia
🔑Retrograde menstruation is considered the predominant mechanism.
ncbi.nlm.nih.gov/pmc/articles/P…
4/
Thoracic endometriosis (TE) is actually the most common non-abdominal site of involvement.
TE also represents the main cause/risk factor for catamenial pneumothorax (CP, 60-90%).
pubmed.ncbi.nlm.nih.gov/21685141/
Thoracic endometriosis (TE) is actually the most common non-abdominal site of involvement.
TE also represents the main cause/risk factor for catamenial pneumothorax (CP, 60-90%).
pubmed.ncbi.nlm.nih.gov/21685141/
5/
Before we return to our original question and examine the right-sided laterality of catamenial pneumothoraces, we need to understand why thoracic endometriosis leads to pneumothorax in the first place.
The main theory involves pleural disruption.
onlinelibrary.wiley.com/doi/epdf/10.10…
Before we return to our original question and examine the right-sided laterality of catamenial pneumothoraces, we need to understand why thoracic endometriosis leads to pneumothorax in the first place.
The main theory involves pleural disruption.
onlinelibrary.wiley.com/doi/epdf/10.10…
6/
Endometrial cells undergo structural changes during the secretory phase of the menstrual cycle, in a process called decidualization.
🔑 Decidualized pleural endometrial implants can disrupt the pleura and lead to pneumothorax (and hemothorax).
pubmed.ncbi.nlm.nih.gov/15753644/
Endometrial cells undergo structural changes during the secretory phase of the menstrual cycle, in a process called decidualization.
🔑 Decidualized pleural endometrial implants can disrupt the pleura and lead to pneumothorax (and hemothorax).
pubmed.ncbi.nlm.nih.gov/15753644/
7/
A 1982 case series reported endometriosis-related diaphragmatic defects in 4 women w/ CP, theorizing that entrained abdominal air w/ menstruation entered the thorax.
But menstruation doesn't cause pneumoperitoneum so this theory is less plausible.
pubmed.ncbi.nlm.nih.gov/6978025/
A 1982 case series reported endometriosis-related diaphragmatic defects in 4 women w/ CP, theorizing that entrained abdominal air w/ menstruation entered the thorax.
But menstruation doesn't cause pneumoperitoneum so this theory is less plausible.
pubmed.ncbi.nlm.nih.gov/6978025/
8/
Now that we've looked at mechanism, let's return to the curious but consistent laterality to catamenial pneumothoraces, as referenced in tweet #1.
💥Nearly 90% occur in the right hemithorax.
Why?
pubmed.ncbi.nlm.nih.gov/8629650/
Now that we've looked at mechanism, let's return to the curious but consistent laterality to catamenial pneumothoraces, as referenced in tweet #1.
💥Nearly 90% occur in the right hemithorax.
Why?
pubmed.ncbi.nlm.nih.gov/8629650/
9/
Another way to ask this question is, why does thoracic endometriosis almost always involve the right hemithorax?
Let's examine the leading theory.
Another way to ask this question is, why does thoracic endometriosis almost always involve the right hemithorax?
Let's examine the leading theory.
10/
It's important to note that most women w/ thoracic endometriosis have abdominopelvic involvement.
⚡️Thoracic endometriosis is thus thought to usually result from transit of endometrial cells from the abdomen into and across the diaphragm.
pubmed.ncbi.nlm.nih.gov/8629650/
It's important to note that most women w/ thoracic endometriosis have abdominopelvic involvement.
⚡️Thoracic endometriosis is thus thought to usually result from transit of endometrial cells from the abdomen into and across the diaphragm.
pubmed.ncbi.nlm.nih.gov/8629650/
11/
Why do ectopic endometrial cells mostly land on the right hemidiaphragm?
Peritoneal fluid actually circulates in a clockwise fashion, up the right paracolic gutter to the subphrenic space.
This was first documented in 1970 via peritoneography.
pubmed.ncbi.nlm.nih.gov/5442658/
Why do ectopic endometrial cells mostly land on the right hemidiaphragm?
Peritoneal fluid actually circulates in a clockwise fashion, up the right paracolic gutter to the subphrenic space.
This was first documented in 1970 via peritoneography.
pubmed.ncbi.nlm.nih.gov/5442658/
12/
Clockwise intraperitoneal flow results from several factors:
🔺 Pressure gradients between the upper/lower abdomen (upward flow)
🔺 Ascending colonic peristalsis (upward flow)
🔺 Anatomic constraints (clockwise direction)
pubmed.ncbi.nlm.nih.gov/18119801/
Clockwise intraperitoneal flow results from several factors:
🔺 Pressure gradients between the upper/lower abdomen (upward flow)
🔺 Ascending colonic peristalsis (upward flow)
🔺 Anatomic constraints (clockwise direction)
pubmed.ncbi.nlm.nih.gov/18119801/
13/
Diaphragmatic contraction acts like a pump, decreasing pressures under the diaphragm (compared to the lower abdomen).
⚡️This pressure gradient draws peritoneal fluid up toward the diaphragm.
⚡️Ascending colon peristalsis also draws fluid upward.
pubmed.ncbi.nlm.nih.gov/18119801/
Diaphragmatic contraction acts like a pump, decreasing pressures under the diaphragm (compared to the lower abdomen).
⚡️This pressure gradient draws peritoneal fluid up toward the diaphragm.
⚡️Ascending colon peristalsis also draws fluid upward.
pubmed.ncbi.nlm.nih.gov/18119801/
14/
Upward flowing fluid is blocked by the falciform ligament and transverse/sigmoid colon (which are intraperitoneal).
This creates clockwise flow and a tendency for endometrial cells to implant on the right hemidiaphragm and enter the right hemithorax.
onlinelibrary.wiley.com/doi/epdf/10.10…
Upward flowing fluid is blocked by the falciform ligament and transverse/sigmoid colon (which are intraperitoneal).
This creates clockwise flow and a tendency for endometrial cells to implant on the right hemidiaphragm and enter the right hemithorax.
onlinelibrary.wiley.com/doi/epdf/10.10…
15/
So to recap catamenial pneumothorax (CP) mechanism:
1⃣Retrograde menstruation ➡️ abdominopelvic endometriosis
2⃣Clockwise abdominal fluid flow ➡️ endometrial cells first reach right hemidiaphragm
3⃣Endometrial implants spread into the thorax and disrupt the pleura ➡️CP
So to recap catamenial pneumothorax (CP) mechanism:
1⃣Retrograde menstruation ➡️ abdominopelvic endometriosis
2⃣Clockwise abdominal fluid flow ➡️ endometrial cells first reach right hemidiaphragm
3⃣Endometrial implants spread into the thorax and disrupt the pleura ➡️CP
16/
@tony_breu has also discussed this association in a previous tweetorial.
He noted how clockwise abdominal fluid flow contributes to the right-sided predominance of hepatic hydrothorax and Meig's syndrome (ovarian fibroma leading to pleural effusion).
@tony_breu has also discussed this association in a previous tweetorial.
He noted how clockwise abdominal fluid flow contributes to the right-sided predominance of hepatic hydrothorax and Meig's syndrome (ovarian fibroma leading to pleural effusion).
https://twitter.com/tony_breu/status/1086725328201007105?s=20
SUMMARY
🫁 Catamenial pneumothorax results from thoracic endometriosis and is almost always right-sided
🫁 Endometriosis can lead to pleural disruption, causing pneumothorax during menstruation
🫁 Right-sided propensity results from clockwise peritoneal fluid flow
🫁 Catamenial pneumothorax results from thoracic endometriosis and is almost always right-sided
🫁 Endometriosis can lead to pleural disruption, causing pneumothorax during menstruation
🫁 Right-sided propensity results from clockwise peritoneal fluid flow
Thank you so much to Drs. @louise_p_king, @ash_bo21 and @helenjkmorgan for providing thoughtful, insightful peer review!
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