1. Three worst kinds of abdominal pain- obstruction of a hollow viscous leading to spasm and intermittent increase in interluminal pressure (as it attempts to push through obstruction): nephrolithiasis, cholelithiasis, labor.
2. Don't forget that abdominal pain can be referred pelvic pain: esp in children, as they can be shy about talking about it, you need to examine GU/pelvic structures to rule out things like testicular torsion. Testicular pain after a sporting event-- likely just local trauma, manage with pain medication and observation, don't miss a torsion, which needs to go emergently to OR. Torsion can happen after sporting events as well, rule it out with a doppler
3. Pain with any movement ("I felt every bump on the ride here") = peritoneal irritation. The logic is that it's caused by passage of some non-sterile, pro-inflammatory contents into the peritoneal cavity; adhesions form quickly to contain the effluent; these adhesions are initially made of fibrin, which needs time to form. The peritoneal process stops GI motility (ileus) and stops the person from moving (severe pain with movement) to buy time for the fibrin to form.
4. DDx of peritoneal irritation, "rebound, guarding":
-Foregut: perforated gastric ulcer (very classic rebound/guarding exam), pancreatitis, cholecystitis
-Midgut/hindgut: appendicitis +/- rupture, bowel perforation, necrotic bowel,  diverticulitis +/- perforation,
-Pelvic: PID, ectopic, ruptured functional (or other) ovarian cyst (can be irritating to peritoneum)
-Systemic: spontaneous bacterial peritonitis, DKA (can cause abdominal pain), familial mediterranean fever (AD, polyserositis-- pleura, peritoneum; diagnosis with peritoneal bx, treat with colchicine)
5. Diagnosing appendicitis, relative constants: 
-Anorexia: present in almost all patients. If your patient is hungry, or has eaten recently, they are unlikely to have appendicitis
-Slow onset
-Vomiting/diarrhea not a significant component. If they describe these symptoms as starting first, and the abdominal pain as later, think of other etiologies.
-No history of similar symptoms.
6. Diagnosing appendicitis, what labs/imaging to order: 
-CBC, UA (r/o pyelo), pregnancy test (r/o ectopic), amylase/lipase/LFTs (r/o pancreatitis, cholecystitis)
-Gradient ultrasound if they can tolerate it-- many people can't. The u/s can't see through air, and there's often a lot of air in the cecum-- so you have to push pretty hard on the abdomen with the u/s probe to get a good imaging appendix and this is highly uncomfortable.
-CT: you will see the appendix coming off cecum, see if it is enlarged, edematous; look for fat stranding around it (normal CT fat, sort of a greyish ground glass background; fat stranding is when it sort of clumps into grey strands interspersed with grey background.
7. Surgical management of acute abdomen
-You have to weigh the risk of a sitting on an acute abdomen vs the morbidity of a negative ex-lap. Some people wait for signs of systemic infection (elevated white count, fever) in addition to an abdominal exam suggestive of acute abdomen.
-In people who may not be able to tolerate sepsis (sickle cell patients, immunocompromised), it may be worth it to go the OR earlier. People with sickle cell also unfortunately have more complications from big abdominal surgeries-- more susceptible to post-operative hypoxia, for example.
-You can find the appendix because its where the colonic tinea come together, forming a ring of longitudinal muscles around it.
-When you take the appendix, ligate the appendiceal aa in the mesoappendix.
8. Appendicitis in an older person- you have to rule out cancer. Appendicitis has a bimodal distribution: it's high in children (from before preteen years to 20s) with lymphoid follicle proliferation (appendix has prominent lymphoid follicles). It's also high in older adults, but the cause there is usually cancer-- it can be hard to detect intraop because inflammation around the appendix and cecum can lead to induration that hides a tumor to palpation. So remove the appendix, and then make sure to follow up with a colonoscopy weeks later when the inflammation has died down.
9. Hypotension in a young woman is a ruptured ectopic pregnancy until proven otherwise. 
10. Group A strep skin infections tend to cause local and systemic symptoms; strep agalactiae (aka GBS) can cause local infection without systemic signs.