Small intestine disease

Jejunum - - - Jejunum and Ileum Figure

• 40% of small intestine
• Few large vascular arcades (loops)
• Long vasa recta
• Large, tall, and closely packed plicae circulares
• Less fat in mesentery than ileum
• Locus of maximum water (90%) and nutrient absorption, except for B12, bile acids, iron, and folate
• 95% of water absorbed

• Ileum - - - Jejunum and Ileum Figure

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  60% of small intestine Many small vascular arcades (loops) Short vasa recta Large, low, and sparse plicae circulares, none distal More fat in mesentery than jejunum Maximum absorption of nonconjugated bile acids, with conjugated bile acids absorbed in terminal ileum B12 and folate maximally absorbed in terminal ileum Endocrine Gut Functions Top Cholecystokinin (CCK): secreted by cells of proximal intestine Secretin: secreted by S cells of proximal intestine Motilin: secreted by M cells of proximal intestine Somatostatin (SMS): secreted by D cells throughout gut Peptide YY (PYY): secreted by L cells of distal intestine Glucagon-like peptide 2 (GLP-2): secreted by L cells of distal intestine   Diverticulectomy: most common treatment for uncomplicated diverticulitis Segmental resection indicated for complicated diverticulitis, neck <1/3 ileal diameter, or inflammation of the base

   

Prostate disease

•  Prostate anatomy
• Supported anteriorly by puboprostatic ligaments, central portions of the pubococcygeus, part of the levator ani muscles (anterior pelvic diaphragm)
• Supported inferiorly by the urogenital diaphragm (transversus perinei muscle and fascia), through which the urethra passes

• Aspects of TURP	Top
  Post-TURP Syndrome: hyponatremia secondary to irrigation; can precipitate seizures and cerebral edema Most common site of primary carcinoma: posterior lobe Most common site of distal metastasis: bone, with osteoblastic lesions showing increased density on CT and radiograph Increases in serum alkaline phosphatase seen with extracapsular carcinoma and metastases

   

  Staging and Treatment ↓

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  Tumor/node/metastasis (TNM) system used Gleason scoring system: additional scoring (1-5) from well differentiated (least aggressive) to poorly differentiated (most aggressive) Transrectal ultrasonography (TRUS) can provide an accurate image of the gland and guide needle biopsies CT can provide evidence of prostatic pathoanatomy, lymphadenopathy, and metastases Optimal treatment for localized prostate cancer remains controversial Intracapsular tumors, no metastases (on T1 and T2 MRI): irradiation, radical prostatectomy with pelvic lymph node excision, or no treatment depending on age, specifics Extracapsular tumors with metastases: hormonal treatment with luteinizing hormone releasing hormone blocker or testosterone blockers, potential orchiectomy; irradiation for pain of bony metastases, chemotherapy for hormone-resistant disease “Chemical castration”: luteinizing hormone releasing hormone (LHRH) antagonists suppress testosterone production in androgen-dependent tumors LHRH antagonists are also called GnRH antagonists (gonadotropin releasing hormone blockers) Alternatives or complements to prostatectomy: x-ray or particle beam therapy, brachytherapy (implanted radiation sources), and cryotherapy

Pancreatic Disease

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Functional Anatomy ↓ Tubuloacinar gland structure with a variety of cell types, including intermingled Islets of Langerhans Parasympathetic and sympathetic nerves are distributed to islets and acini Cells’ secretions are controlled by endocrine and autonomic nervous activities
- Exocrine Functions ↓
Mediated by secretin and cholecystokinin formed by duodenal and jejunal epithelium Acinar cells secrete amylase, lipase, trypsinogen, chymotrypsinogen, carboxypeptidase, and Cl- Ductal cells secrete HCO3- Some secretomotor input comes from vagal parasympathetic fibers
- Endocrine Functions ↓	Top
Alpha cells secrete glucagon Beta cells (central islets) secrete insulin Delta cells secrete somatostatin F or PP cells secrete pancreatic polypeptide Islet cells also produce vasoactive intestinal peptide (VIP), serotonin, neuropeptide Y, and gastrin releasing peptide (GRP) 5 fluorouracil (5-FU) and streptozocin chemotherapy work well for all Insulinoma Most common islet cell tumor, >85% benign symptoms (Whipple’s triad): fasting hypoglycemia, hypoglycemic symptoms (catechol surge, elevated heart rate, sweating), relieved by glucose

Kidney Disease

Intrarenal Arteries and Renal Segments

Ureter Fibromuscular tube with mucosa Upper: renal pelvis to upper border of sacrum Middle: overlies sacrum Lower: border of sacrum to bladder Blood supply: upper from renal arteries, middle from ovarian or testicular arteries, lower from vesical arteries Innervation of Kidneys and Ureters Top Parasympathetic Preganglionic: vagal fibers run through celiac and superior mesenteric plexuses, joining renal nerve plexus for distribution to ganglion cells in renal parenchyma, pelvis, and ureter Sympathetic Preganglionic: fibers run through splanchnic nerves (especially least), celiac, and superior mesenteric plexuses to synapse in aorticorenal ganglia Postganglionic: fibers distributed to smooth muscle of renal vessels and gomeruli Sensory: segmental visceral afferent fibers run parallel to sympathetic fibers to dorsal root ganglia and spinal segments T11-L2  Renal cell carcinoma (hypernephroma): metastasized to lung (most common) or colon Greatest risk factor: smoking Nephroblastoma (Wilms’ tumor): Rare renal malignant tumor of early childhood: 8/million incidence Tumor cells produce renin, leading to hypertension  Associated with hypospadias, cryptorchidism, ocular malformations  Most common secondary renal tumor: breast metastasis

Hernia

Nerves Near the Spermatic Cord ↓

Iliohypogastric: superficial if seen Ilioinguinal: typically superficial to cord Genitofemoral: usually posterior to cord  Inguinal Hernia  Indirect Passes through deep (internal) inguinal ring, inguinal canal, and finally through superficial (external) inguinal ring; follows course of spermatic cord Typically congenital, associated with a persistence of the fetal processus vaginalis (peritoneal tract accompanying the descending testis) Direct Passes directly through posterior wall of inguinal canal, through defect in transversalis fascia, within Hesselbach’s triangle

Esophageal Disease

ANATOMY OF THE ESOPHAGUS\

•  cricopharyngeus, the first region of anatomical constriction

Retropharyngeal danger space: possibility of infection spread ing retroesophageally into the thorax Tunica Muscularis Inner circular: continuous superiorly with the circumferential fibers of the inferior pharyngeal constrictor Outer longitudinal: upper third is striated (voluntary muscle) like the pharynx; middle third is a combination of striated and smooth muscle; lowest third is smooth muscle Innervation - - - - - - Figure The esophageal nerve plexus is composed of vagal afferent and efferent, sympathetic efferent, and segmental sensory components Parasympathetic preganglionic fibers Upper (cervical) portion from the recurrent laryngeal nerve Thoracic portion from the vagus via the pulmonary plexus (peribronchial) Ganglion cells located in myenteric plexuses Sympathetic postganglionic fibers Via nerves from cervical and thoracic chains From cervical ganglia and thoracic ganglia Sensory fibers (visceral afferent) Vagus: stretch, chemoreceptor, nociceptor; to vagal ganglia Segmental (parallel to sympathetics) with spinal nerves; to cervical and thoracic dorsal root ganglia   CLINICAL CORRELATES Zenker’s Diverticulum Top False (posterior) diverticulum Occurs between the cricopharyngeus and the rest of the inferior constrictor Caused by increased swallowing pressure Symptoms: upper esophageal dysphagia, halitosis, choking Treatment: cricopharyngeal myotomy, resected or suspended (without removal of diverticulum) via left cervical incision Clinical Correlates ↑ Traction Diverticulum True diverticulum, typically lateral Caused by granulomatous disease, chronic inflammation, or tumor Typically in mid-esophagus

Gastroduodenal Disease and Anatomy

Gastric Microscopic Anatomy	Top
Mucosa Epithelium Mucus-secreting cardia glands Oxyntic glands in the fundus and body Chief cells secrete pepsinogen Parietal cells secrete H+ and intrinsic factor Antrum and pylorus glands Both secrete HC03 and mucus G cells release gastrin D cells secrete somatostatin, inhibiting release of gastrin and H+

anatomy of the Duodenum
Most fixed portion of small bowel, surrounds head of the pancreas

Duodenal Microscopic Anatomy	Top
Mucosa Epithelium: enterocytes (absorptive), goblet cells, Paneth cells, enterochromaffin cells Lamina propria: contains Peyer’s patches (lymphoid aggregations with B cells in germinal centers and T cell in interfollicular zones) Muscularis mucosa Water and nutrients absorbed across the mucosa

• Inner Surface
  • Mucosal surface area specializations: microvilli, villi, plica circulares (valvulae conniventes)
  • Total absorptive surface: 200-550 cm2

 

Gastroduodenal Embryology

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Stomach has two mesenteries during development Dorsal mesogastrium, attached to the greater curvature, grows very redundant, overlaps, and becomes the greater omentum Ventral mesogastrium, part of the original septum transversum, becomes the following Lesser omentum (hepatogastric ligament) Peritoneal serosa of liver, gallbladder Falciform ligament, with embedded round ligament of the liver Greater curvature is initially dorsal, then the stomach rotates along its longitudinal axis until the dorsal curve lies to the left Stomach also rotates around an axis through the gastroesophageal junction, until the greater curvature lies in its final left inferolateral position Duodenum also rotates with the stomach, as well as around an anteroposterior axis, so that it surrounds the pancreas First two parts of the duodenum (down to the bile duct), the terminal portion of the foregut: supplied by the celiac axis Lower second through fourth parts of the duodenum, the initial segment of the midgut: supplied by the proximal superior mesenteric artery

Innervation

• Parasympathetic
  • Left vagal trunk lies anterior as it crosses the gastroesophageal junction and runs anteriorly along the lesser curvature toward the duodenum
  • Right vagal trunk lies posterior as it crosses the gastroesophageal junction and runs posteriorly along the lesser curvature toward the duodenum
  • Ganglion cells are located in myenteric (Auerbach’s) and submucosal (Meissner’s) plexuses in stomach and duodenum
• Sympathetic
  • Preganglionic fibers from T8-T10 lateral column distributed via splanchnic nerves
  • Postganglionic fibers are distributed from ganglion cells in celiac and superior mesenteric ganglia, traveling along respective arterial branches
• Sensory fibers (general visceral afferent)
  • Vagal afferents, including stretch, chemo-, and "satiety" receptors
  • Segmental afferents travel back parallel to sympathetics, through the celiac and superior mesenteric plexuses and the splanchnic nerves to thoracic spinal nerves, dorsal root ganglia, and spinal segments

 Gastritis

• Chronic
  • Type A: in fundus, associated with autoimmune disease and pernicious anemia
  • Type B: in antrum, associated with Helicobacter pylori

Peptic Ulcer :70%-80% in lesser curvature of the stomach
Hiatal Hernia - - - - - - Figure Top Type I: dilation of hiatus with sliding hernia; most common, may be associated with GERD, although most Type I patients do not reflux Type II: paraesophageal, hole in diaphragm next to the esophagus; symptoms - dysphagia, chest pain, early satiety Type III: combined Type IV: entire stomach in thorax, other organs may be included (e.g., spleen or colon)