Tuesday, June 7, 2011

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
    • 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
      • 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
     

Friday, June 3, 2011

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
    • 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 ↓
    • 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

Thursday, June 2, 2011

Pancreatic Disease


  •  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 ↓
  • 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
    • 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

Wednesday, June 1, 2011

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
  •  

Monday, May 30, 2011

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
    • 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
    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
  • 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
  • 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
  • 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
  • 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)