Anatomy to Biostats

Question 0

What is the cause of direct hernias?
Where are they located in respect to the inferior epigastric veins?
What demographic do they occur in?
What ring do they protrude through?
What fascia are they covered by?

Answer 0

Cause: weakness of the transversalis fascia (acquired or chronic injury)
Location: medial
Demographic: older men

Protrude through: external (superficial) inguinal ring ONLY
Covered by: external spermatic fascia ONLY

Question 1

What is the cause of indirect hernias?
Where are they located in respect to the inferior epigastric veins?
What demographic do they occur in?
What ring do they protrude through?
What fascia are they covered by?

Answer 1

Cause: persistent processus vaginalis and failure of internal inguinal ring to close
Location: lateral
Demographic: infant males

Protrude through: external (superficial) AND internal (deep) inguinal rings
Covered by: all THREE layers of spermatic fascia (external spermatic, cremasteric, internal spermatic)

Question 2

Hawthorne effect? Pygmalion effect? Berkson bias?

Answer 2

Hawthorne - groups know they’re being studied and act differently

Pygmalion - self-fulfilling prophecy - belief in efficacy by researcher changes outcome

Berkson - bias from studying only hospital pts as the control group

Question 3

What does the left gonadal (testicular/ovarian) vein drain directly into? The right?

Answer 3

Left gonadal vein -> left renal vein -> IVC
(obstruction of left renal vein leads to varicocele in men)

Right gonadal vein -> IVC

Question 4

What is a hydrocele and where is the fluid confined? How does it form?

Answer 4

serous fluid that collects in the tunica vaginalis

occurs when communication between processus vaginalis and peritoneum (normally obliterated) remains patent – allows fluid from peritoneum to accumulate in scrotum

Question 5

What ligament must be ligated during oophorectomy or removal of ovarian mass to avoid excessive bleeding during surgery?

Answer 5

suspensory ligament (infundibulopelvic ligament)
contains the ovarian vessels

Question 6

What region of the urethra is most at risk in pelvic fracture? In saddle injuries?

Answer 6

Pelvic fracture – injury to posterior urethra
(membranous segment most at risk - weakest segment vs. prostatic)

Saddle injury – injury to anterior urethra

Presents with full bladder sensation, inability to void, high-riding boggy prostate, blood at urethral meatus.

Question 7

What vessels will best aid surgeon in distinguishing indirect from direct hernia?

Answer 7

inferior epigastric vessels

medial - direct
lateral - indirect
“MDs don’t LIe”

Question 8

Enlarged lymph nodes in the inguinal area – what do they drain?

Answer 8

all skin from the umbilicus down drains to superficial inguinal lymph nodes
(including anus up to dentate/pectinate line, but excluding posterior calf)

Question 9

Which LNs do lymph from the testes drain to?

Answer 9

abdominal aortic lymph nodes

Question 10

What drugs can be used in treatment of BPH?

Answer 10

alpha-1 adrenergic blockers (relax smooth muscle in bladder neck)
5alpha reductase inhibitors (prevent conversion of testosterone to DHT)

Question 11

Difference in stratified analysis with confounding vs. effect modification scenario?

Answer 11

Confounding:
stratified analysis looking at external variable will give large, nonsignficant P values (suggesting effect was due to confounding variable)

Effect modification:
stratified analysis looking at external variable will still give a significant effect for risk between stratified groups (suggests external variable modifies the effect of a real relationship)

Question 12

LN drainage of a superficial scrotal mass? A testicular mass?

Answer 12

scrotum drains to superficial inguinal lymph nodes

testes drain to the para-aortic lymph nodes