Medications that constrict blood vessels or otherwise alter blood flow can reduce the amount of blood that reaches the colon. An operation involving the aorta (the body’s largest artery) or the blood vessels that supply the bowel may have resulted in damage that affects blood flow to the colon. A hernia, tumor or scar tissue in the colon can impede blood flow. Blood flow to the colon can be compromised by conditions such as vascular disease, congestive heart failure, heart rhythm disorders, blood-clotting problems, sickle cell anemia or diabetes. For unknown reasons, IBS-which is characterized by cramping, abdominal pain, bloating, gas, diarrhea and constipation-appears to triple the risk for colon stroke. Though people of both sexes do get colon strokes, the condition occurs somewhat more often among women. Risk generally increases with age, with about 90% of colon strokes occurring after age 60. Some of these risk factors are not under your control-but simply knowing that you have them can motivate you to keep a watchful eye out for possible symptoms of a colon stroke. Though no one knows exactly why one person might suffer a colon stroke while another person doesn’t, various factors are known to increase risk. Why is that so dangerous? Because even though most colon strokes are not life-threatening, about 10% to 15% of patients develop bowel perforation (a hole in the bowel) or gangrene (tissue death caused by insufficient blood supply)-conditions that require immediate surgery if the patient is to survive. Brandt, MD, a professor in the department of medicine, gastroenterology and liver diseases at Montefiore Medical Center in the Bronx, New York, who has conducted extensive research on colon stroke. “The patient may end up being treated for the wrong disease, while the real problem goes undetected,” said Lawrence J. Circular Stroke Shading Circular stroke pencil shadingĬircular stroke shading is less common but can still be very useful for certain effects (smoke for example).Problem: These symptoms often are confused with those of other digestive disorders, including gastroenteritis, a broad term for irritation or infection of the digestive tract (including food poisoning)… infectious colitis (colon inflammation caused by infection) and Crohn’s disease (an inflammatory bowel disease). Smooth or blended pencil shading can be useful in certain cases where you do not want there to be visible pencil strokes. The advantage of curved crosshatch strokes is that they tend to look more natural. Similar to the non-overlapping curved strokes curved crosshatch strokes can be used for shading drawings of curved objects. Crosshatch Curved Stroke Shading Curved crosshatch stroke pencil shading Curved Stroke Shading One direction pencil shading strokesĬurved shading strokes are useful for shading objects with a curved surface where you want to emphasize the shape of that object. Crosshatch Shading Crosshatch stroke pencil shadingĬrosshatching is a shading technique where stroke is applied in two directions with overlapping strokes and is probably the most commonly used shading style. When making these try and keep them some distance apart so that the individual lines stay visible. Straight one directional strokes are the most basic shading technique. It can be useful for drawing with pencils, markers, pens and other mediums including digital drawing.įor a practical and very basic application of some of the strokes in these examples you can see:Įgg Step by Step Basic Shading Tutorial One Directional Strokes One direction stroke pencil shading strokes This tutorial explains several different ways to apply strokes when shading.
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