Block 42 Flashcards
Fetal hydronephrosis
Commonly detected in the second trimister during routine ultrasonographic anatomy survey.
- the finding is usually transient or clinically insignificant as the fetal renal pelvis has high compliance and can accomodate large volumes of urine.
- the most common pathologic cause of unilateral fetal hydronephrosis is a narrowing or kinking of the proximal ureter at uretopelvic junction.
- newborns presents with abdominal mass reflecting an enlarged kidney.
- the uteropelvic junction is the last segment of the fetal ureter to canalize. The pathogenesis of UPJ obstruction may involve failure of this canalization through abnormal development of circular musculature and/or collagen fibers.
Infleuenza vaccines mechanism
They include inactivated( killed) vaccine administered by injection and a live attenuated vaccine given by nasal spray.
Each seasonal influenza vaccine contains antigens from 3 or 4 infleuenza A and B virus strains.
-inactivated version of infleuenza vaccine function mainly by inducing neutralizing antibodies against the hemagglutinin antigen in selected viral strains.
-upon subsequent exposure to infleuenza these antibodies inhibit binding of hemagglutinin to sialylated receptors on host cell membrane. This prevents the live virus from entering cells via endocytosis.
Huntington pathogenesis
- transcriptional repression is one of the mechanism by which mutated huntington is thought to cause disease.
- regulation of transcription occurs in part due to the presence of histones, which can undergo variety of modifications that affects the accessibility of the genome for transcription.
- acetylation of histones weakens the DNA-histone bond and makes DNA segments more accessible for transcription factors and RNA polymerase, enhancing gene transcription.
- in huntington disease abnormal Huntington causes increased histone deacetylation, sliencing the genes necessary for neuronal survival.
- huntington is due to CAG repeats in the gene coding for huntington. Expansion of the protein polyglutamine region results in gain of function that leads to pathological interaction with other proteins including various transcription factors.
Heme synthesis enzyme diseases
- Sideronlastic anemia —> ∂-aminolevulinic acid synthase
- Lead poisining : —> ∂-aminoluvulinic acid dehydratase and ferrochelatase.
- acute intermittent porphyria —> prophobilinogen deaminase
- Porphyria cutanea tarda —> uroporphyrinogen decarboxylase.
Porphyria cutanea tarda
The most common disorder of porphyrin synthesis.
Its caused by uroporphtinogen decarboxylase deficiency, which is either inherited or acquired, manifesting in the presence of iron and of susceptibility factors.
-photosensetivity presents as vesicles and blister formation on sun exposed areas as well as edema, pruritus, pain and erythemia.
Acute intermittent porphyria symptoms
- painful abdomen
- port wine colored urine
- polyneuropathy
- psychological disturbances
- precipitated by drugs (cp450 inducers), alcohol, starvation
Common peroneal nerve injury is due to
Due to its superficial location its susceptible to injury .
-neck of the fibula fracture
Pudendal nerve block location
When performing PN block , the ischial spines should be palpated intravaginally and the anesthetic should be injected medially in very close proximity to the ischial spine through sacrospinous ligament.-other important structure that are present in that area include the internal pudendal artery and inferior gluteal artery which run medial to the PN. Injection in one of those can lead to hematoma or arrythmia (if lidocaine is used)
Lateral femoral cutaneous nerve (meralgia paresthetica)
Courses deep to the inguinal ligament to innervate the anterolateral thigh skin. Its commonly injured during hyperflexion of the thigh in the lithotomy position for pelvic surgery or vaginal delivery. Complications include anterior and lateral thigh numbness.
-meralgia paresthetica can be caused by obstruction of the LFCN in the inguinal ligament.
PPI mechanism of action
It inhibit H/K ATPase > decreasing concentraion of HCL in gastic lumen
Tetrodotoxin
Its a potent neurotoxin found in pufferfish, functions by blocking the voltage gated sodium channels in nerve cell membranes. Inhibits passive transport of sodium.
Decreased physical workload at immobilzation leads to
-as a result, the skeletal muscle fibers in his leg decreased in size leading to disuse atrophy. Atrophy is tissue loss due to cellular death or reduced cell size.
Nonreactive pupils to light stimulation following cardiac arrest indicates
-anoxic damage to the brainstem at the level of the upper midbrain.
Pupillary reflex
during normal pupillary reflex, the retina as well as the optic nerve and tract transmit the light stimulus to the midbrain at the level of superior colliculus where its recieved by the pretectal nucleus and subsequently relayed to bilateral edinger westphal nuclei.
-these nuclei subsequently projects preganglionic parasympathetic fibers through the oculomotor nerve to the cilliary ganglion —> sphincter pupillae muscle
During oophrectomy what ligament should be ligated
The suspensory ligament of the ovary (infundibulopelvic ligament). It contains the ovarian artery, vein, lymphatics and nerves.
Increased myocardial oxygen during exercise can only be achieved through a corresponding increase in coronary blood flow.
The most important ones are adenosine and nitric oxide involved in coronary blood flow autoregulation
- adenosine, a product of ATP metabolism, acts as a vasodilatory element in the small coronary arterioles.
- nitric oxide is created by and released from the endothelial cells in the coronary vasculature. Its synthesized by arginine and O2 by endothelial NO synthase and is released from the coronary endothelium in response to neurotransmitters, platelt product, thrombin, histamine, bradykinin and endothillin.
- NO is also released in response to pulsatile stretch and flow shear stress in the coronary arteries. It is major regulator or flow mediated vasodilation in large arteries and periarteriolar vessels.
Mannitol side effects
- mannitol works by rapidly increasing plasma or tubular fluid omolality which causes water to move from interstitial space into the vascular space or tubular lumen. In kidney it primarily acts on PCT.
- in the brain, water redistribution from the tissues into the plasma helps to reduce cerberal edema and intracranial pressure.
- overaggressive treatment with osmotic diuretics can lead to excessive volume depletion and eventual hypernatremia in certain patients. One of the more severe toxicities of aggressive osmotic diuretic therapy is pulmonary edema, caused by the rapid rise in volume that can also increase the overall hydrostatic pressure in the vasculature.
Clumps of erythroid precurosr cells in liver and spleen is characterestic of
Chronic hemolysis- indicated extramedullary hematopoiesis due to hemolytic anemia (eg .ß-thalassemia)
Maxillary overgrowth, frontal bossing and hepatosplenomegaly is seen in
ß-thalasemia
Villous adenoma vs tubular
- villous Are often large, sessile and can have velvety or cauliflower like projections. It can secrete large quantities of watery mucus leading to secretory diarrhea, hypovolemia and electrolytes abnormalities.
- By contrast, tubular adenomas are composed of dysplastic colonic mucosal cells that form tube shaped glands and tend to be smaller and pudenculated.
- tubuvillous adenoma contains mixture of these 2 types
- villous adenoma are more likely to undergo malignant transformation.
Metyhlmalonic acidemia
Autosomal recessive organic acidemia resulting from complete or partial deficiency of methylmalonyl CoA mutase.
- catabolism of isoleucine, valine theronine, methionine and odd chain fatty acid normally leads to propionyl CoA formation which is then converted to methylmalonyl CoA by biotin dependent carboxylation.
- methylmalonyl CoA is then converted to succinyl-coa and enter TCA.
- mutation in methylmalonyl CoA mutase results in buildup of methylmalonic acid leading to acidosis, hypoglycemia (increased metabolic rate leading to increased glucose utilization and inhibition of gluconeogenesis by organic acids).
- hypoglycemia leads to ketones formation.
- organic amino acid directly inhibit urea cycle leading to hyperammonemia.
- it manifest as hypotonia, lathergy, vomiting and respiratory distress in neonatal period.
- diagnosis is confirmed by the presence of elevated urine methylamlonic acid and propionic acid.
Propionic acidemia
Deficiency in propionyl-CoA carboxylase, results in hyperammonemia, hypoglycemia and metabolic acidosis, although it doesnt display elevated levels of urine methylmalonic acid.
Neuroblastoma
Pathogenesis: neural crest origin, involves adrenal medulla, sympathetic chain.
Clinical features:
1. Median age <2
2. Abdominal mass (most often involving adrenal galnd)
3. Periorbital ecchymosis
4. Spinal cord compression from epidural invasion “dumbbell tumor”
5. Opsoclonus-myoclonus syndrome(conjugate eye movements and involuntary jerking movements of the trunk and limbs)
Diagnostic findings:
Elevated catecholamines metabolites, small round blue cells on histology, N-myc gene amplification.
-biopsy of the mass is diagnostic and reveals small round blue cell and homer wright rosettes.
Acute hepatitis due to inhaled anesthetics
- halongenated anesthetics modulate various neuronal ion channels, leading to CNS depression. They are metabolized by hepatic CP450 system by which they are converted to reactive intermediates that can directly injure the liver of lead to immune mediated hepatocellular damage.
- halothone hepatitis typically present 2 days to 3 weeks after medication exposure with fever, nausea, jaundice, tender hepatomegaly and elevated aminotransferases and billirubin levels.
- liver can show centrilobular hepatic necrosis that indistingushible from viral hepatitis.
- drugs include (enflurane, isoflurane, sevoflurane, desflurane, halothane)
Analgesic nephropathy
- NSAIDs can cause renal failure if taken in large amounts over extended periods.
- affected patients typically have modest elevation in serum creatinine, mild proteinuria and evidence of tubular dysfunction( polyuria, nocturia)
- microscopic hematuria and sterile pyuria may also be seen on urinalysis.
- NSAIDs concentrates in the renal medulla along the medularry osmotic gradient with higher levels in the papillae.
- prolonged use leads to chronic interstitial nephritis seen as patchy interstitial inflammation with subsequent fibrosis, tubular atrophy, papillary necrosis and scarring, and caliceal architecture distortion.
- Ca+ may deposit in areas of chronic inflammation and this calcification is visible on renal imaging. NSAID also decrease prostaglandins synthesis causing constriction of medullary vasa recta and ischemic papillary necrosis.
Vascular endothelium secrete what substance to inhibit platelet aggregation
Prostacyclin (prostaglandin I2)
Erythema infectiosum
Benign childhood illness caused by parvovirus b19, SS DNA virus.
Lacy reticular rash follows the slapped cheeck rash, spreading over the trunk and extremities. The rash may result from immune complex deposition, the timing of which coincides with increasing levels of serum virus specific IgM and IgG.
-B19 replicates in erythrocytes precursor in the bone marrow. These cells express blood group P antigen.
